KR20110107718A - Positive active material for rechargeable lithium battery, cathod for rechargeable lithium battery, rechargeable lithium battery and method for manufacturing thereof - Google Patents

Abstract

The present invention relates to a cathode active material for a lithium secondary battery, a cathode for a lithium secondary battery, a lithium secondary battery, and a manufacturing method thereof, wherein the particle diameter is 20 to 1, and includes primary particles including a compound represented by the following Chemical Formula 1 having a particle diameter of 0.1 to 1 μm. By using the positive electrode active material for a lithium secondary battery including secondary particles having a thickness of 60 μm, a positive electrode active material showing high energy density may be provided, and a lithium secondary battery having excellent cycling characteristics may be manufactured.
[Formula 1]
LiMO ₂
(In Formula 1, M is Ni, Co, Mn or a combination thereof.)

Description

POSITIVE ACTIVE MATERIAL FOR RECHARGEABLE LITHIUM BATTERY, CATHOD FOR RECHARGEABLE LITHIUM BATTERY, RECHARGEABLE LITHIUM BATTERY AND METHOD FOR MANUFACTURING THEREOF}

The present invention relates to a cathode active material for a lithium secondary battery, a cathode for a lithium secondary battery, a lithium secondary battery, and a method of manufacturing the same.

Recently, with the trend toward miniaturization and light weight of portable electronic devices, the need for high performance and high capacity of batteries used as power sources for these devices is increasing.

Cells generate electricity by using materials that can electrochemically react to the positive and negative electrodes. A typical example of such a battery is a lithium secondary battery that generates electric energy by a change in chemical potential when lithium ions are intercalated / deintercalated at a positive electrode and a negative electrode.

The lithium secondary battery is manufactured by using a material capable of reversible intercalation / deintercalation of lithium ions as a positive electrode and a negative electrode active material, and filling an organic electrolyte or a polymer electrolyte between the positive electrode and the negative electrode.

As a cathode active material of a lithium secondary battery, a lithium composite metal compound is used. Examples thereof include a composite of LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiNi _{1- x} Co _x O ₂ (0 <x <1), and LiMnO ₂ . Metal oxides are being studied.

Among the cathode active materials, Mn-based cathode active materials such as LiMn ₂ O ₄ and LiMnO ₂ are easy to synthesize, are relatively inexpensive, have the best thermal stability compared to other active materials when overcharged, and have low environmental pollution and are attractive. Although it has a disadvantage, the capacity is small.

In addition, LiNiO ₂ exhibits the highest discharge capacity of battery characteristics among the cathode active materials mentioned above, but has a disadvantage in that it is difficult to synthesize. In addition, the high oxidation state of nickel causes a decrease in battery and electrode life, and there is a problem of severe self discharge and inferior reversibility. In addition, it is difficult to commercialize the stability is not perfect.

LiCoO ₂ is currently common in active materials with a particle size of about 10 μm, but this does not guarantee sufficient energy density.

It is to provide a lithium secondary battery having excellent cycling stability by providing a positive electrode active material having a high energy density.

In one aspect, the present invention provides a cathode active material for a lithium secondary battery including secondary particles having a particle size of 20 to 60 μm, including primary particles including a compound represented by the following Chemical Formula 1 having a particle size of 0.1 to 1 μm. do.

[Formula 1]

LiMO ₂

(In Formula 1, M is Ni, Co, Mn or a combination thereof.)

The compound represented by Chemical Formula 1 may be LiCoO ₂ .

In another aspect of the invention, the positive electrode active material for a lithium secondary battery comprising a secondary particle having a particle size of 20 to 60㎛, consisting of primary particles comprising a compound represented by the following formula 1 having a particle diameter of 0.1 to 1㎛ Provided is a positive electrode, the positive electrode provides a lithium secondary battery positive electrode having an electrode density of 3.5 to 4.5g / cc.

[Formula 1]

LiMO ₂

(In Formula 1, M is Ni, Co, Mn or a combination thereof.)

The compound represented by Chemical Formula 1 may be LiCoO ₂ .

The anode may have a void volume of 15 to 30% by volume.

The positive electrode may further include a binder and a conductive material in addition to the positive electrode active material, and may include 88 to 96% by weight of the positive electrode active material, 2 to 6% by weight of the binder, and 2 to 6% by weight of the conductive material.

In another aspect of the present invention, the cathode active material for a lithium secondary battery including secondary particles having a particle size of 20 to 60㎛, consisting of primary particles comprising a compound represented by the following formula 1 having a particle diameter of 0.1 to 1㎛ Anode comprising a; A negative electrode including a negative electrode active material; A separator separating the positive electrode and the negative electrode; And it provides a lithium secondary battery comprising an electrolyte.

[Formula 1]

LiMO ₂

(In Formula 1, M is Ni, Co, Mn or a combination thereof.)

The compound represented by Chemical Formula 1 may be LiCoO ₂ .

The anode may have an electrode density of 3.5 to 4.5 g / cc.

The anode may have a void volume of 15 to 30% by volume.

The positive electrode may further include a binder and a conductive material in addition to the positive electrode active material, and may include 88 to 96% by weight of the positive electrode active material, 2 to 6% by weight of the binder, and 2 to 6% by weight of the conductive material.

The lithium secondary battery may have a capacity retention rate of 70% or more relative to the initial capacity after 290 cycles of charge and discharge at 7C rate.

In another aspect of the invention, (a) preparing a compound represented by the following formula (1) of the plate-shape of the long axis of 50 to 250nm in length; (b) laminating the compound in the crucible; And (c) primary particles comprising a compound represented by the following Chemical Formula 1 having a particle size of 0.1 to 1 μm under hydrothermal conditions using the compound stacked on the crucible, having a particle size of 20 to 60 μm. It provides a method for producing a cathode active material for a lithium secondary battery comprising the step of preparing a cathode active material comprising secondary particles.

[Formula 1]

LiMO ₂

(In Formula 1, M is Ni, Co, Mn or a combination thereof.)

The compound represented by Chemical Formula 1 may be LiCoO ₂ .

The compound represented by the formula (1) of the plate-shape of 50 to 250nm in length of the long axis of step (a) may be prepared under hydrothermal conditions using a mixture containing M raw material and Li raw material.

(M is Ni, Co, Mn, or a combination thereof.)

The compound represented by the formula (1) of the plate-shape of the long axis of the step (a) is 50 to 250nm by the method of annealing the mixture containing the M raw material and the Li raw material at a temperature of 150 to 250 ℃ It may be prepared.

(M is Ni, Co, Mn, or a combination thereof.)

The positive electrode active material including secondary particles having a particle size of 20 to 60 μm, consisting of primary particles including the compound represented by the following Chemical Formula 1 having a particle size of 0.1 to 1 μm in the step (c), is laminated on the crucible The compound represented by Formula 1 may be prepared by a method of annealing at 800 to 1000 ℃.

[Formula 1]

LiMO ₂

(In Formula 1, M is Ni, Co, Mn or a combination thereof.)

The crucible of step (b) may be an alumina crucible or a zirconia crucible.

In another aspect of the invention, (a) preparing a compound represented by the following formula (1) of the plate-shape of the long axis of 50 to 250nm in length; (b) laminating the compound in the crucible; (c) 2 having a particle size of 20 to 60 μm, consisting of primary particles comprising a compound represented by the following Chemical Formula 1 having a particle size of 0.1 to 1 μm under hydrothermal conditions using the compound stacked on the crucible. Preparing a positive electrode active material including tea particles; (d) mixing the cathode active material, the binder, and the conductive material to prepare a cathode active material slurry; (e) coating the cathode active material slurry on at least one surface of a cathode current collector; And (f) drying and rolling the coated positive electrode active material slurry to provide a method of manufacturing a positive electrode for a lithium secondary battery.

[Formula 1]

LiMO ₂

(In Formula 1, M is Ni, Co, Mn or a combination thereof.)

The compound represented by Chemical Formula 1 may be LiCoO ₂ .

The compound represented by the formula (1) of the plate-shape of 50 to 250nm in length of the long axis of step (a) may be prepared under hydrothermal conditions using a mixture containing M raw material and Li raw material.

(M is Ni, Co, Mn, or a combination thereof.)

The compound represented by the formula (1) of the plate-shape of the long axis of the step (a) is 50 to 250nm by the method of annealing the mixture containing the M raw material and the Li raw material at a temperature of 150 to 250 ℃ It may be prepared.

(M is Ni, Co, Mn, or a combination thereof.)

The positive electrode active material including secondary particles having a particle size of 20 to 60 μm, consisting of primary particles including the compound represented by the following Chemical Formula 1 having a particle size of 0.1 to 1 μm in the step (c), is laminated on the crucible The compound represented by Formula 1 may be prepared by a method of annealing at 800 to 1000 ℃.

[Formula 1]

LiMO ₂

(In Formula 1, M is Ni, Co, Mn or a combination thereof.)

The electrode density of the prepared anode may be 3.5 to 4.5g / cc.

The pore volume of the prepared positive electrode may be 15 to 30% by volume.

By providing a cathode active material showing a high energy density, it is possible to manufacture a lithium secondary battery showing excellent cycling characteristics.

1 is XRD pattern analysis data of Example 1.
Figure 2a is a SEM photograph of the LiCoO ₂ material of the plate shape prepared in Example 1.
Figure 2b is a TEM photograph of the plate-shaped LiCoO ₂ material prepared in Example 1.
Figure 2c is a SEM photograph of the secondary particles of size 40㎛ prepared in Example 1.
FIG. 2d is a SEM photograph of secondary particles having a size of 40 μm prepared in Example 1. FIG.
3 is a graph showing the characteristics at different C rates of the half cells prepared in Example 4. FIG.
4 is a discharge capacity experimental data according to the cycle of Example 4, Example 5, Comparative Example 8 and Comparative Example 9.
5 is an energy density experiment data according to the cycle of Example 4, Example 5, Comparative Example 8, Comparative Example 9, Comparative Example 10 and Comparative Example 11.
6A is a graph showing the battery characteristics of Example 6 at C rates under different conditions.
6B is a graph showing the discharge capacity of the battery of Example 6 with cycles at 7C;
7A is XRD analysis data of a positive electrode active material after 290 cycles of Example 6. FIG.
7B is a high resolution electron microscopy (HREM) photograph of the positive electrode active material after 290 cycles of Example 6. FIG.

Hereinafter, embodiments of the present invention will be described in detail. However, it should be understood that the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

The energy density of the positive electrode of a lithium secondary battery is related to the electrode density. In other words, low electrode density means low energy density. When a secondary battery is used in a mobile device, since the use time of the mobile device is an important characteristic, it is very important to improve the energy density of the positive electrode among the secondary battery electrodes.

In other words, a method for improving the electrode density of the anode can be considered as a method for improving the energy density. As a method of improving the electrode density of the positive electrode, there is a method of simply increasing the size of particles of the positive electrode active material.

However, the positive electrode active material of which the particle size is simply increased may decrease the area of contact with the electrode, which may worsen the rate characteristic of the battery.

Therefore, the best way to improve both the rate characteristics and the electrode density is to use the positive electrode active material in the form of secondary particles composed of sub-micro sized particles.

In one embodiment of the present invention, the positive electrode active material for a lithium secondary battery including secondary particles having a particle size of 20 to 60㎛, consisting of primary particles comprising a compound represented by the following formula (1) having a particle size of 0.1 to 1㎛ to provide.

[Formula 1]

LiMO ₂

(In Formula 1, M is Ni, Co, Mn or a combination thereof.)

Sub-micro primary particles of 0.1 to 1 μm have a large surface area in contact with the electrode, which can promote the rapid movement of lithium ions into the anode. In addition, the positive electrode active material, which is a secondary particle having a thickness of 20 to 60 μm, formed of the primary particles, may have an improved electrode density and a decrease in pore volume, thereby facilitating movement of electrolytes and ions, and thus not deteriorating rate characteristics.

The compound represented by Chemical Formula 1 may be LiCoO ₂ , and M provided above is not necessarily limited to Co. However, for convenience of description, Co will be described below.

In general, LiCoO ₂ is widely used as a cathode active material of a battery such as a mobile device because of the excellent electrode density and energy potential, LiCoO ₂ cathode active material of this size has not been reported to date.

In another embodiment of the present invention, the cathode active material for a lithium secondary battery including secondary particles having a particle size of 20 to 60㎛, consisting of primary particles comprising the compound represented by Formula 1 having a particle size of 0.1 to 1㎛ A positive electrode comprising a, the positive electrode provides a lithium secondary battery positive electrode having an electrode density of 3.5 to 4.5g / cc.

The description related to the particle size is omitted because it is the same as mentioned in the cathode active material of the embodiment of the present invention.

When the electrode is manufactured using the cathode active material, the electrode density may be 3.5 to 4.5 g / cc. As described above, when the electrode density is improved, the energy density is also improved, thereby improving the life of the battery.

While achieving the same electrode density as in the above range, the anode may have a pore volume of 15 to 30% by volume. When the void volume is in the above range, rate characteristics of a commercially available battery can be obtained. Pore volumes smaller than this range cause low penetration of the electrolyte into the electrode, thereby reducing the rate characteristic of the cell.

The positive electrode may further include a binder and a conductive material in addition to the positive electrode active material.

The binder includes, for example, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene, mixtures thereof, and the like.

Examples of the conductive material include carbon black, graphite, and metal powder.

In addition, the positive electrode may include 88 to 96% by weight of the positive electrode active material, 2 to 6% by weight of the binder and 2 to 6% by weight of the conductive material. The above range must be satisfied to satisfy the above-mentioned range of void volume.

The positive electrode may be prepared by mixing the positive electrode active material, the conductive material, the binder, and a solvent to prepare a positive electrode active material slurry, and then directly coating and drying the aluminum current collector. Alternatively, the cathode active material slurry may be cast on a separate support, and then the film obtained by peeling from the support may be manufactured by laminating on an aluminum current collector.

As the solvent, N-methylpyrrolidone, acetone, tetrahydrofuran, decane and the like can be used.

In another embodiment of the present invention, the lithium secondary battery positive electrode comprising secondary particles having a particle diameter of 20 to 60 ㎛ made of primary particles comprising a compound represented by the formula (1) having a particle diameter of 0.1 to 1 ㎛ Provided is a lithium secondary battery including a positive electrode including an active material, a negative electrode including a negative electrode active material, a separator to isolate the positive electrode and the negative electrode, and an electrolyte solution.

The description related to the positive electrode is omitted as it is the same as mentioned in the positive electrode which is an embodiment of the present invention.

Like the positive electrode, the negative electrode is mixed with a negative electrode active material, a binder, and a solvent to prepare a negative electrode active material slurry, which is directly coated on a copper current collector or cast on a separate support and peeled from the support to a negative electrode active material film on the copper current collector. It is prepared by lamination. At this time, the negative electrode active material slurry may further contain a conductive material if necessary.

As the negative electrode active material, a material capable of intercalating / deintercalating lithium is used, and for example, lithium metal, lithium alloy, coke, artificial graphite, natural graphite, organic polymer compound combustor, carbon fiber, or the like is used. . In addition, a conductive material, a binder, and a solvent are used similarly to the case of the positive electrode mentioned above.

The separator may be used as long as it is commonly used in a lithium secondary battery. For example, polyethylene, polypropylene, polyvinylidene fluoride or two or more multilayer films thereof may be used, and a polyethylene / polypropylene two-layer separator, It goes without saying that a mixed multilayer film such as polyethylene / polypropylene / polyethylene three-layer separator, polypropylene / polyethylene / polypropylene three-layer separator and the like can be used.

As the electrolyte to be charged in the lithium secondary battery, a non-aqueous electrolyte or a known solid electrolyte may be used, and a lithium salt is used.

Although the solvent of the said non-aqueous electrolyte is not specifically limited, Cyclic carbonate, such as ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate; Chain carbonates such as dimethyl carbonate, methyl ethyl carbonate and diethyl carbonate; Esters such as methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate and γ-butyrolactone; Ethers such as 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1,2-dioxane and 2-methyltetrahydrofuran; Nitriles such as acetonitrile; Amides, such as dimethylformamide, etc. can be used. These can be used individually or in combination of multiple. In particular, a mixed solvent of a cyclic carbonate and a linear carbonate can be preferably used.

As the electrolyte, a gel polymer electrolyte in which an electrolyte solution is impregnated with a polymer electrolyte such as polyethylene oxide or polyacrylonitrile, or an inorganic solid electrolyte such as LiI or Li ₃ N can be used.

The lithium salt is 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 , LiSbF ₆ , LiAlO ₄ , LiAlCl ₄ , One selected from the group consisting of LiCl and LiI is possible.

The lithium secondary battery may have a capacity retention of more than 70% of the initial capacity after 290 cycles of charge and discharge at a 7C rate. That is, the lithium secondary battery as described above has a high energy density and excellent cycling stability as described above even under conditions such as 7C rate. That is, it can be seen that even after a large number of cycles, the cathode active material is free of damage to the microstructure. Data on this will be reviewed in more detail in the following examples.

In another embodiment of the present invention, (a) preparing a compound represented by the formula (1) in the form of a plate having a long axis of 50 to 250nm, (b) laminating the compound in the crucible and (c) Secondary particles having a particle size of 20 to 60 μm using primary compounds including the compound represented by Formula 1 having a particle size of 0.1 to 1 μm in hydrothermal conditions using the compound stacked in the crucible It provides a method for producing a cathode active material for a lithium secondary battery comprising the step of preparing a positive electrode active material comprising.

The compound represented by the formula (1) of the plate-shape of 50 to 250nm in length of the long axis of step (a) can be prepared under hydrothermal conditions using a mixture containing M raw material and Li raw material.

(M is Ni, Co, Mn, or a combination thereof.)

The Co raw material is at least one selected from the group consisting of Co (NO ₃ ) ₂ · 6H ₂ O, CoCl ₂ and CoSO ₄ , The Li raw material is at least one selected from the group consisting of LiOH, LiCl and LiNO ₃ Can be.

The Ni raw material may be at least one selected from the group consisting of Ni (NO ₃ ) ₂ .6H ₂ O, NiCl _2, and NiO ₄ .

The Mn raw material may be at least one selected from the group consisting of Mn (NO ₃ ) ₂ .6H ₂ O, MnCl ₂ and MnSO ₄ .

The compound represented by the formula (1) of the plate-shape of the long axis of the step (a) is 50 to 250nm in length, 60 to 80 at a temperature of 150 to 250 ℃ in a mixture containing the M raw material and Li raw material in an autoclave By annealing for a time. To satisfy the above range can be prepared a compound represented by the formula (1) of the plate-shape of 50 to 250nm long.

The positive electrode active material including secondary particles having a particle size of 20 to 60 μm, including primary particles including the compound represented by Formula 1 having a particle size of 0.1 to 1 μm in the step (c), is laminated to the crucible The compound represented by the following formula (1) may be by the method of annealing at 800 to 1000 ℃ for 2 to 5 hours, the above range must be satisfied to prepare the cathode active material.

Such hydrothermal synthesis is available on a mass scale and is a very simple method that can be used directly in industry.

The crucible of step (b) may be an alumina crucible or a zirconia crucible.

According to another embodiment of the present invention, (a) preparing a compound represented by the formula (1) in the form of a long axis of 50 to 250nm, (b) laminating the compound in the crucible and (c ) Secondary particles having a particle diameter of 20 to 60 μm, consisting of primary particles containing the compound represented by Formula 1 having a particle size of 0.1 to 1 μm under hydrothermal conditions using the compound stacked on the crucible. Preparing a positive electrode active material comprising a, (d) mixing the positive electrode active material, a binder and a conductive material to prepare a positive electrode active material slurry, (e) coating the positive electrode active material slurry on at least one surface of a positive electrode current collector And (f) drying and rolling the coated positive electrode active material slurry to provide a method of manufacturing a positive electrode for a lithium secondary battery.

Since the substrate related to the positive electrode active material is the same as the method of manufacturing the positive electrode active material of the embodiment of the present invention, it will be omitted.

The electrode density of the prepared anode may be 3.5 to 4.5g / cc. As described above, when the electrode density is improved, the energy density is also improved, thereby improving the life of the battery.

The pore volume of the prepared positive electrode may be 15 to 30% by volume. When the void volume is in the above range, rate characteristics of a commercially available battery can be obtained. Pore volumes smaller than this range cause low penetration of the electrolyte into the electrode, thereby reducing the rate characteristic of the cell.

The positive electrode may further include a binder and a conductive material in addition to the positive electrode active material.

Such binders include, for example, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene, mixtures thereof, and the like.

Examples of the conductive material include carbon black, graphite, metal powder, and the like.

In addition, the positive electrode may include 88 to 96% by weight of the positive electrode active material, 2 to 6% by weight of the binder and 2 to 6% by weight of the conductive material. The above range must be satisfied to satisfy the above-mentioned range of void volume.

The positive electrode may be prepared by mixing the positive electrode active material, the conductive material, the binder, and a solvent to prepare a positive electrode active material slurry, and then directly coating and drying the aluminum current collector. Alternatively, the cathode active material slurry may be cast on a separate support, and then the film obtained by peeling from the support may be manufactured by laminating on an aluminum current collector.

The solvent may be N-methylpyrrolidone, acetone, tetrahydrofuran, decane and the like.

Hereinafter, preferred examples and comparative examples of the present invention are described. However, the following examples are only preferred examples of the present invention and the present invention is not limited to the following examples.

Example

1. Preparation of positive electrode active material

Example  1: Preparation of Positive Electrode Active Material

Long axis length is 200 nm Phosphorus LiCoO ₂  of  Produce

Co (NO ₃ ) ₂ · 6H ₂ O was used as the Co raw material, and LiOH was used as the Li raw material. Equivalent amounts of Co (NO ₃ ) ₂ .6H ₂ O were dissolved in 1-hexanol, followed by addition of LiOH and oleylamine. All procedures were accompanied by strong stirring (batch reactor size 500 g).

The mixture was then transferred to an autoclave and annealed at 200 ° C. for 72 hours to form a powder.

The powder was then cooled to room temperature (25 ° C.) and unreacted LiOH was removed by three washes with water and two washes with ethanol.

The washed powder was vacuum dried at 200 ° C. for 24 hours. The powder size was 200 nm (length of long axis) and the shape was plate-shaped.

Preparation of the positive electrode active material in the form of secondary particles of 40 ㎛

The powder thus prepared was densely stacked in a 0.5 liter alumina crucible and then annealed at 900 ° C. for 3 hours. By the above procedure, a 40 μm secondary particle type LiCoO ₂ positive electrode active material obtained by collecting primary particles having a diameter of 1 μm was obtained.

Comparative example  1: 10 μm size LiCoO ₂  Preparation of Cathode Active Material

Co ₃ O ₄ (5 μm, Alpha, USA) and LiCO ₃ (Alpha, USA) were stirred in a 1: 1 equivalent ratio and then calcined at 1000 ° C. for 3 hours to cool to prepare a 10 μm LiCoO ₂ cathode active material. .

Comparative example  2: carbon coated LiFePO ₄  Preparation of Cathode Active Material

FeC ₂ O ₄ .2H ₂ O, (NH ₄ ) ₂ HPO ₄ and LiNO ₃ were equivalently completely dissolved in water.

Then, LiFePO ₄ powder was formed by heating at 700 ° C. for 10 hours under mixed gas conditions of H ₂ / N ₂ (10/90 vol%).

After cooling the formed powder to room temperature (25 ℃), the sucrose aqueous solution was mixed with the powder.

After annealing at 700 ° C. for 5 hours, the sucrose was transformed into amorphous carbon and coated on the powder.

The final carbon content of the prepared carbon-coated LiFePO ₄ positive electrode active material was 1.5% by weight.

Comparative example  3: LiNi _{0 .8} Co _{0 .15} Al _{0 .05} O ₂  Preparation of Cathode Active Material

In diameter 10㎛ Ecopro Inc. _{(Korea) LiNi 0 .8 Co 0 .15 Al} 0 .05 O was the ₂ positive active material.

2. Manufacturing of Anode

Example  2: preparation of the anode ( Void volume : 20 volumes %, Electrode density: 4.1 g / cc )

In the preparation of the positive electrode active material slurry for producing a positive electrode, the positive electrode active material was used as the positive electrode active material prepared in Example 1, the binder was used poly (vinylidene fluoride) (poly (vinylidene fluoride), PVDF), Super P carbon black was used as the conductive material, and N-methyl-2-pyrrolidene (NMP) was used as the solvent.

The mixing ratio of the slurry was 92: 4: 4 wt% (active material: binder: conductive material).

Thereafter, the slurry was directly coated and dried on an aluminum current collector to prepare a positive electrode. After drying, the electrode plate was rolled twice using a roll press (roll press, 1 ton / cm ² ).

The pore volume of the prepared anode, measured using a porosity meter (Mercury porosimeter, Micromeritics Pore Sizer 9320), was 20% by volume, and the electrode density was 4.1g / cc. The electrode density of 4.1 g / cc corresponds to 3 Wh / cc, which corresponds to an excellent value.

Example  3: production of anode ( Void volume : 28 volumes %, Electrode density: 3.5 g / cc )

A positive electrode was prepared in the same manner as in Example 2, except that the mixing ratio of the slurry was 88: 6: 6 wt% (active material: binder: conductive material).

The pore volume of the prepared positive electrode was 28% by volume, and the electrode density was 3.5g / cc.

Comparative example  4: preparation of the anode ( Void volume 20 volumes %, Electrode density 3.5g / cc )

The positive electrode active material in the same manner as in Example 2 except for using the positive electrode active material prepared in Comparative Example 1 and the mixing ratio of the slurry to 96: 2: 2% by weight (active material: binder: conductive material) Was prepared.

The pore volume of the prepared positive electrode was 20% by volume, and the electrode density was 3.5g / cc.

Comparative example  5: production of anode ( Void volume 15 volumes %, Electrode density 3.8 g / cc )

Except that the positive electrode active material was used in the positive electrode active material prepared in Comparative Example 1, the mixing ratio of the slurry was 96: 2: 2% by weight (active material: binder: conductive material) and the rolling was performed three times. A positive electrode was prepared in the same manner as in Example 2.

Comparative example  6: Preparation of the anode Void volume 20 volumes %, Electrode density 2.6 g / cc )

The same method as in Example 2, except that the positive electrode active material using the positive electrode active material prepared in Comparative Example 2 and the mixing ratio of the slurry to 90: 3: 7% by weight (active material: binder: conductive material). A positive electrode was prepared.

The pore volume of the prepared positive electrode was 20% by volume, and the electrode density was 2.6g / cc.

Comparative example  7: Preparation of anode Void volume 20 volumes %, Electrode density 3.3g / cc )

The same method as in Example 2, except that the positive electrode active material using the positive electrode active material prepared in Comparative Example 3 and the mixing ratio of the slurry to 92: 4: 4% by weight (active material: binder: conductive material) A positive electrode was prepared.

The pore volume of the prepared anode was 20% by volume and the electrode density was 3.3g / cc.

3. Preparation of Half Cells

Example  4: Preparation of Half Cells

Coin-shaped half cells (2016-size) were fabricated in Example 2, the anode, lithium-counter electrode, 15 mm thick micro-porous polyethylene separator and ethylene carbonate (EC) / dimethyl carbonate (DMC). (1: 1 volume%, LG Chem., Korea) was prepared using 1M LiPF ₆ electrolyte.

Example  5: Preparation of Half Cells

A half cell was manufactured in the same manner as in Example 4, except that the positive electrode prepared in Example 3 was used instead of the positive electrode prepared in Example 2.

Comparative example  8: Preparation of Half Cells

A half cell was manufactured in the same manner as in Example 4, except that the positive electrode prepared in Comparative Example 4 was used instead of the positive electrode prepared in Example 2.

Comparative example  9: Preparation of Half Cells

A half cell was manufactured in the same manner as in Example 4, except that the positive electrode prepared in Comparative Example 5 was used instead of the positive electrode prepared in Example 2.

Comparative example  10: Preparation of Half Cells

A half cell was manufactured in the same manner as in Example 4, except that the positive electrode prepared in Comparative Example 6 was used instead of the positive electrode prepared in Example 2.

Comparative example  11: Preparation of Half Cells

A half cell was prepared in the same manner as in Example 4 except that the positive electrode prepared in Comparative Example 7 was used instead of the positive electrode prepared in Example 2.

4. Preparation of Pouch Type Lithium Secondary Battery

Example  6: Preparation of Pouch Type Lithium Secondary Battery

A natural graphite negative electrode having a dimension ratio of 1.15: 1 in the positive electrode, the negative electrode to the positive electrode prepared in Example 2 (in this ratio, lithium deposition does not occur on the negative electrode at 4.35 V (vs. graphite)), polyethylene separator, ethylene A pouch-type lithium secondary battery was manufactured using an electrolyte in which 1 mol of LiPF ₆ was mixed with carbonate and diethyl carbonate (3: 4 by volume).

The manufacturing process was carried out in a dry-room (containing less than 100 ppm moisture).

The lithium secondary battery had a size of 20 cm ² (5 cm long, 4 cm short), a height of 0.3 cm, and a standard capacity of 820 mAh.

Experimental Example

One. XRD  pattern

The XRD patterns of the plate-shaped LiCoO ₂ material prepared in Example 1 and the secondary particles having a size of 40 μm were analyzed, respectively.

The result can be seen in FIG.

As can be seen in FIG. 1, however, the integral ratio of the LiCoO ₂ material, which is plate-shaped, is 2.4, while the integral ratio of secondary particles 003 to 104, which are 40 μm in size, is 3.5. This means that the 40 μm sized secondary particles annealed at 900 ° C. exhibit very strong orientation of the structure along the c-axis.

The measured lattice constants a and c of the plate-shaped LiCoO ₂ materials were 2.813 Å and 14.042 각각, respectively (c / a = 4.991). The a and c values represent the distance between the inner layer (1/3 of the c-axis in the hexagonal unit cell) and the a-axis of the neighboring layer (metal-metal distance) of the inner layer in the hexagonal cell. The secondary particles having a size of 40 μm show a = 2.810 and c = 14.072 (c / a = 5.01), indicating very large deviations along the c-axis.

This means that lithium promotes more intercalation at the 3a site. Changes in lattice constant (viz. C / a ratio) resulted in an increase in crystal orientation along the c-axis of 900. ^o seems to be due to annealing in C.

2. SEM  And TEM  Picture

2A and 2B are SEM and TEM images of the plate-shaped LiCoO ₂ material prepared in Example 1 above.

This shows that the length of the major axis is a plate with a size of less than 250 nm.

2c and 2d are SEM images of the secondary particles having a size of 40 μm prepared in Example 1.

During the annealing process, the plate-shaped LiCoO ₂ material aggregates into large secondary particles and each plate-shaped LiCoO ₂ material turns into particles of 1 μm size. The size of the secondary particles is about 40 μm. As known to those skilled in the art, with respect to LiCoO ₂ positive electrode active material, this kind of form has not been reported.

3. Example  Characteristic experiment of the cell prepared in 4

3 is a graph showing the characteristics at different C rates of the half cells prepared in Example 4. FIG.

The first discharge capacity of Example 4 was 3 to 4.5V and 185 mAh / g at 0.2C rate. In addition, the initial discharge capacity was reduced to 173 and 165 mAh / g at 5 and 7C rates.

4. Example  4, Example  5, Comparative example  8 and Comparative example  Discharge Capacity Experiment with 9 Cycles

4 is discharge data experimental data according to cycles of Example 4, Example 5, Comparative Example 8 and Comparative Example 9.

Example 4 and Example 5 showed the same discharge capacity of 185mAh / g at 0.2C regardless of the electrode density.

In Comparative Examples 8 and 9, the discharge capacity is drastically decreased due to the increase in the number of cycles at 7C. However, it is understood that Examples 4 and 5 are significantly smaller in the reduction range. This shows stability to the cycles of Examples 4 and 5.

5. Example  4, Example  5, Comparative example  8, Comparative example  9, Comparative example  10 and Comparative example  Energy density experiment according to 11 cycles

5 is energy density experimental data according to cycles of Example 4, Example 5, Comparative Example 8, Comparative Example 9, Comparative Example 10 and Comparative Example 11. Experimental conditions are 7C rate.

In the case where the rate condition is 7C, the difference in characteristics of each cell is wider than in the case of 5C. Thus, the experiment was performed at 7C, where the conditions are more severe.

After 48 cycles, the holding capacity of Example 4 is 149 mAh / g, which corresponds to a 2.1 Wh / cc energy density.

On the other hand, the first discharge capacity of Comparative Example 9 was 133 mAh / g, after 48 cycles, it was sharply reduced to 25 mAh / g. This corresponds to 0.35 Wh / cc. This result indicates that after 40 cycles, the case of Example 4 has an energy density 5.7 times larger than that of Comparative Example 9.

The energy density of Example 5 after 40 cycles was 2.3 Wh / cc, which was higher than that of Example 4. However, Comparative Example 8 with the same electrode density was found to have an energy density of 1.25 Wh / cc after 40 cycles.

In addition, the energy density of Comparative Example 10 during the first discharge was 0.9 Wh / cc (110 mAh / g), and decreased to 0.75 Wh / cc after 30 cycles. Meanwhile, Comparative Example 11 exhibited 1.5 Wh / cc (125 mAh / g) at the first discharge, and the energy density after 30 cycles was reduced to 1.25 Wh / cc.

It was found that the stability of the energy density according to the cycles of Examples 4 and 5 was remarkably excellent.

6. Example  Evaluation of characteristics of the battery manufactured in 6

6A is a graph showing battery characteristics at different C rates under different conditions.

As can be seen in FIG. 6A, the discharge capacities of the battery prepared in Example 6 were 169, 164 and 158 mAh / g at 0.2, 3 and 7C rates, respectively. That is, it can be seen that the discharge capacity at 0.2C was maintained at 93% even at 7C.

Figure 6b is a graph showing the discharge capacity according to the cycle at 7C conditions.

The discharge capacity after 290 cycles corresponds to 78% of the discharge capacity of the first cycle.

No such good rate characteristics have been reported tested under these demanding conditions.

7. Example  Structural analysis of the positive electrode active material after 290 cycles of 6

In order to analyze the structural destruction of the positive electrode active material in the positive electrode according to the cycle, the positive electrode after 290 cycles of Example 6 was extracted, and XRD and HREM images were analyzed. The analysis results are shown in FIGS. 7A and 7B.

7A is XRD analysis data of the positive electrode active material after 290 cycles of Example 6. FIG.

The XRD pattern did not show the shape of the secondary phase, and the intensity ratio of (003) to (104) was measured as 3.2. This is similar to the value of the initial electrode. The results indicate that there is no damage to the microstructure of the active material during the cycle.

7B is a HREM photograph of the positive electrode active material after 290 cycles of Example 6. FIG. 7B shows a diffraction pattern of the cathode active material.

The HREM photograph clearly shows well developed stratification and d spacing value of 4.31 mm 3. The d spacing value of 4.31 ms corresponds to the (003) plane of the hexagonal stratification.

The inset of FIG. 7B shows the presence of a complete hexagonal single crystal phase.

Thus, the decrease in cell characteristics appears to be attributable to other factors such as, for example, graphite, electrolytes and cell balance.

The present invention is not limited to the above embodiments, but may be manufactured in various forms, and a person skilled in the art to which the present invention pertains has another specific form without changing the technical spirit or essential features of the present invention. It will be appreciated that the present invention may be practiced as. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (25)

A cathode active material for lithium secondary battery comprising secondary particles having a particle size of 20 to 60 μm, including primary particles including a compound represented by the following Chemical Formula 1 having a particle diameter of 0.1 to 1 μm.
[Formula 1]
LiMO ₂
(In Formula 1, M is Ni, Co, Mn or a combination thereof.)
The method of claim 1,
The compound represented by Formula 1 is LiCoO ₂ positive electrode active material for a lithium secondary battery.
A cathode including a cathode active material for a lithium secondary battery including secondary particles having a particle diameter of 20 to 60 μm, including primary particles including a compound represented by the following Chemical Formula 1 having a particle diameter of 0.1 to 1 μm,
The positive electrode is a lithium secondary battery positive electrode having an electrode density of 3.5 to 4.5g / cc.
[Formula 1]
LiMO ₂
(In Formula 1, M is Ni, Co, Mn or a combination thereof.)
The method of claim 3, wherein
The compound represented by Formula 1 is LiCoO ₂ positive electrode for a lithium secondary battery.
The method of claim 3, wherein
The positive electrode is a lithium secondary battery positive electrode having a void volume of 15 to 30% by volume.
The method of claim 3, wherein
The positive electrode further includes a binder and a conductive material in addition to the positive electrode active material,
88 to 96% by weight of the positive electrode active material, 2 to 6% by weight of the binder and 2 to 6% by weight of the conductive material.
A positive electrode including a positive active material for a lithium secondary battery including secondary particles having a particle diameter of 20 to 60 μm, including primary particles including a compound represented by the following Chemical Formula 1 having a particle diameter of 0.1 to 1 μm;
A negative electrode comprising a negative electrode active material;
A separator separating the positive electrode and the negative electrode; And
Electrolyte solution;
Lithium secondary battery comprising a.
[Formula 1]
LiMO ₂
(In Formula 1, M is Ni, Co, Mn or a combination thereof.)
The method of claim 7, wherein
The compound represented by Formula 1 is LiCoO ₂ It is a lithium secondary battery.
The method of claim 7, wherein
The positive electrode is a lithium secondary battery having an electrode density of 3.5 to 4.5g / cc.
The method of claim 7, wherein
The positive electrode has a pore volume of 15 to 30% by volume lithium secondary battery.
The method of claim 7, wherein
The positive electrode further includes a binder and a conductive material in addition to the positive electrode active material,
88 to 96% by weight of the positive electrode active material, 2 to 6% by weight of the binder and 2 to 6% by weight of the conductive material.
The method of claim 7, wherein
The lithium secondary battery is a lithium secondary battery that has a capacity retention of more than 70% of the initial capacity after 290 cycles of charge and discharge at 7C rate.
(a) preparing a compound represented by the following Chemical Formula 1 having a long axis of 50 to 250 nm in length;
(b) laminating the compound in the crucible; And
(c) 2 having a particle size of 20 to 60 μm, consisting of primary particles comprising a compound represented by the following Chemical Formula 1 having a particle size of 0.1 to 1 μm under hydrothermal conditions using the compound stacked on the crucible. Preparing a positive electrode active material including tea particles;
Method for producing a cathode active material for a lithium secondary battery comprising a.
[Formula 1]
LiMO ₂
(In Formula 1, M is Ni, Co, Mn or a combination thereof.)
The method of claim 13,
The compound represented by Formula 1 is LiCoO _{2 The} method for producing a cathode active material for a lithium secondary battery.
The method of claim 13,
The compound represented by the formula (1) of the plate-shape of 50 to 250nm in length of the long axis of the step (a) is prepared in a hydrothermal condition using a mixture containing M raw material and Li raw material positive electrode for a lithium secondary battery Method for producing an active material.
(M is Ni, Co, Mn, or a combination thereof.)
The method of claim 13,
The compound represented by the formula (1) of the plate-shape of the long axis of the step (a) is 50 to 250nm by the method of annealing the mixture containing the M raw material and the Li raw material at a temperature of 150 to 250 ℃ Method for producing a cathode active material for a lithium secondary battery that is prepared.
(M is Ni, Co, Mn, or a combination thereof.)
The method of claim 13,
The positive electrode active material including secondary particles having a particle size of 20 to 60 μm, consisting of primary particles including the compound represented by the following Chemical Formula 1 having a particle size of 0.1 to 1 μm in the step (c), is laminated on the crucible Method of producing a cathode active material for a lithium secondary battery that is prepared by the method of annealing the compound represented by the following formula (1) at 800 to 1000 ℃.
[Formula 1]
LiMO ₂
(In Formula 1, M is Ni, Co, Mn or a combination thereof.)
The method of claim 13,
The crucible of step (b) is an alumina crucible or zirconia crucible is a method of manufacturing a positive electrode active material for a lithium secondary battery.
(a) preparing a compound represented by the following Chemical Formula 1 having a long axis of 50 to 250 nm in length;
(b) laminating the compound in the crucible;
(c) 2 having a particle size of 20 to 60 μm, consisting of primary particles comprising a compound represented by the following Chemical Formula 1 having a particle size of 0.1 to 1 μm under hydrothermal conditions using the compound stacked on the crucible. Preparing a positive electrode active material including tea particles;
(d) mixing the cathode active material, the binder, and the conductive material to prepare a cathode active material slurry;
(e) coating the cathode active material slurry on at least one surface of a cathode current collector; And
(f) drying and rolling the coated positive electrode active material slurry;
Method for producing a positive electrode for a lithium secondary battery comprising a.
[Formula 1]
LiMO ₂
(In Formula 1, M is Ni, Co, Mn or a combination thereof.)
The method of claim 19,
The compound represented by Formula 1 is LiCoO _{2 The} method for producing a positive electrode for a lithium secondary battery.
The method of claim 19,
The compound represented by the formula (1) of the plate-shape of 50 to 250nm in length of the long axis of the step (a) is prepared in a hydrothermal condition using a mixture containing M raw material and Li raw material positive electrode for a lithium secondary battery Manufacturing method.
(M is Ni, Co, Mn, or a combination thereof.)
The method of claim 19,
The compound represented by the formula (1) of the plate-shape of the long axis of the step (a) is 50 to 250nm by the method of annealing the mixture containing the M raw material and the Li raw material at a temperature of 150 to 250 ℃ Method for producing a positive electrode for a lithium secondary battery will be prepared.
(M is Ni, Co, Mn, or a combination thereof.)
The method of claim 19,
The positive electrode active material including secondary particles having a particle size of 20 to 60 μm, consisting of primary particles including the compound represented by the following Chemical Formula 1 having a particle size of 0.1 to 1 μm in the step (c), is laminated on the crucible Method for producing a positive electrode for a lithium secondary battery which is prepared by the method of annealing the compound represented by the following formula (1) at 800 to 1000 ℃.
[Formula 1]
LiMO ₂
(In Formula 1, M is Ni, Co, Mn or a combination thereof.)
The method of claim 19,
The electrode density of the prepared positive electrode is a manufacturing method of a lithium secondary battery positive electrode that is 3.5 to 4.5g / cc.
The method of claim 19,
Method for producing a cathode for a lithium secondary battery that the pore volume of the prepared positive electrode is 15 to 30% by volume.

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