KR20130058590A - Positive active material for rechargeable lithium battery, method of preparing the same, and rechargeable lithium battery including the same - Google Patents

Abstract

PURPOSE: A positive electrode active material for a lithium secondary battery is provided to improve capacity and electrode density. CONSTITUTION: A positive electrode active material for lithium secondary batteries is provided to include a solid solution represented by chemical formula 1: xLi_2MnO_3·(1-x)LiMO_2. The solid solution includes a primary particle and a secondary particle. The number average particle diameter of the primary particle is 0.5 micron or more. In chemical formula 1, x is as follows, 0.1<=x<=0.6, and M is a metal composite compound represented by chemical formula 2: Mn_aCo_bNi_c where, a, b, and c are as follows, 0.3<=a<=0.5, 0.05<=b<=0.3, 0.3<=c<=0.55, and a+b+c=1. [Reference numerals] (AA) After plasticizing(add molybdate)

Description

A positive electrode active material for a lithium secondary battery, a method of manufacturing the same, and a lithium secondary battery including the same TECHNICAL FIELD

The present disclosure relates to a cathode active material for a lithium secondary battery, a manufacturing method thereof, and a lithium secondary battery including the same.

BACKGROUND ART Lithium ion secondary batteries are required to have high capacities to be used in portable electronic devices such as mobile phones and notebook PCs, automobiles, and the like.

For this purpose, a solid solution of a Li ₂ MnO ₃ · LiMO _{2 type} (M = Co, Ni, etc.) has attracted attention as a cathode material for a lithium ion secondary battery.

The Li ₂ MnO ₃ · LiMO ₂ -based solid solution reported so far has not been found to increase the electrode density like LiCoO ₂ widely used as a positive electrode material for lithium ion secondary batteries. For this reason, when the said solid solution is used as a positive electrode active material, since high capacity of a battery cannot be obtained, it has not reached the practical use stage yet.

In order to improve the conventional electrode density, Japanese Laid-Open Patent Publication No. 2001-155728 increases the particle size of the positive electrode material by increasing the size of the precursor of the positive electrode material or increasing the firing temperature during synthesis of the positive electrode material. A method of making is disclosed. However, although the positive electrode material of large particle diameter can be obtained by the said method, a capacity | capacitance falls and a charge / discharge characteristic deteriorates, and the particle diameter of a positive electrode material and the improvement of a battery characteristic cannot be acquired simultaneously.

In addition, only by changing the manufacturing conditions of the solid solution positive electrode material, that is, the size and firing conditions of the precursor in the above method, the primary particles of the solid solution do not grow but partially sinter, and as a result, the electrode density cannot be increased. As a result, battery characteristics are reduced.

In addition, Japanese Laid-Open Patent Publication No. 2007-042385 discloses a method of forming a high density region in which an active material is contained in a relatively high density and a low density region in which an active material is contained in a relatively low density and increasing the electrode density.

In addition, Japanese Laid-Open Patent Publication No. 2006-086116 discloses a method for improving electrode density using vapor-grown carbon fiber (VGCF).

In addition, Japanese Laid-Open Patent Publication No. 2010-033830 discloses a technique of including active material particles having different particle size distribution as a method of increasing the electrode density of a negative electrode.

However, in the case of using a solid solution anode material, even using these methods, the electrode density could not be sufficiently increased.

In addition, techniques focusing on electrode density are disclosed in Japanese Patent Laid-Open No. 2006-127923, Japanese Patent Laid-Open No. 2010-218884, and Japanese Patent Laid-Open No. 2007-141527.

However, these techniques are not intended to increase the capacity of the battery, but to improve the storage characteristics, the charge and discharge characteristics, and the cycle characteristics, and it is difficult to increase the capacity of the batteries even when these techniques are applied to batteries using solid solution positive electrode materials.

One embodiment of the present invention is to provide a cathode active material for a lithium secondary battery having a high capacity while increasing the electrode density.

Another embodiment of the present invention is to provide a method of manufacturing the positive electrode active material for the lithium secondary battery.

Another embodiment of the present invention is to provide a cathode for a lithium secondary battery comprising the cathode active material.

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

An embodiment of the present invention includes a solid solution represented by Formula 1, wherein the solid solution includes primary particles and secondary particles, and the primary particles of the solid solution have a number average particle diameter of 0.5 μm or more for a lithium secondary battery. It provides a positive electrode active material.

[Formula 1]

xLi ₂ MnO ₃ (1-x) LiMO ₂

(In Formula 1, 0.1≤x≤0.6, M is a metal complex compound represented by the following formula (2)

[Formula 2]

Mn _a Co _b Ni _c

(In Formula 2, 0.3≤a≤0.5, 0.05≤b≤0.3 and 0.3≤c≤0.55, and a + b + c = 1.)

The primary particles of the solid solution may have an average particle diameter of 0.5 to 5 ㎛.

Another embodiment of the present invention comprises the steps of mixing a molybdate salt with at least one selected from a solid solution represented by the formula (1), and a mixture of a precursor and a lithium compound of the solid solution; And calcining the mixture prepared by mixing at a temperature of 750 to 1050 ° C, wherein the molybdate salt is mixed at 5 to 50 parts by mass based on 100 parts by mass of the solid solution or 100 parts by mass of the precursor of the solid solution. Provided is a method of manufacturing a cathode active material for a lithium secondary battery.

The firing may be carried out at a temperature of 600 to 1050 ℃.

The molybdate salt may be mixed in an amount of 3 to 60 parts by mass based on 100 parts by mass of the solid solution or 100 parts by mass of the precursor of the solid solution.

After the calcining, the molybdate may further comprise the step of removing the molybdate salt by washing the mixture prepared by mixing the molybdate salt.

The molybdate salt may include at least one selected from lithium molybdate and sodium molybdate.

Another embodiment of the present invention provides a cathode for a lithium secondary battery including the cathode active material.

The anode may have an electrode density of 2.8 g / cc or more.

According to another embodiment of the present invention, cathode; And a lithium secondary battery comprising the electrolyte.

Other details of the embodiments of the present invention are included in the following detailed description.

By increasing the electrode density of the positive electrode, it is possible to implement a lithium secondary battery having a high capacity.

1A is a SEM photograph of solid solution particles before firing according to Example 1, FIG. 1B is a SEM photograph of solid solution particles after firing according to Example 1, and FIG. 1C is a SEM photograph of solid solution particles after firing according to Comparative Example 1 .
2 is a graph showing initial discharge capacities of lithium secondary batteries of Example 1 and Comparative Example 1. 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.

According to one embodiment, by using the molybdate salt as a sintering accelerator in the production of a positive electrode active material using a solid solution represented by the formula (1), it is possible to increase the diameter of the primary particles of the solid solution without deteriorating the battery characteristics and thus The density can be increased.

[Formula 1]

xLi ₂ MnO ₃ (1-x) LiMO ₂

(In Formula 1, 0.1≤x≤0.6, M includes at least one metal selected from Co, Mn and Ni.)

First, a lithium secondary battery according to one embodiment is described in detail.

The lithium secondary battery has, for example, a rectangular, columnar, coin-shaped, button-shaped, sheet-like, cylindrical, flat plate-like shape, and includes a positive electrode, a negative electrode, an electrolyte solution, and a separator.

The positive electrode includes a current collector and a positive electrode active material layer formed on the current collector, and the positive electrode active material layer includes a positive electrode active material.

As the said electrical power collector, For example, foil, a sheet | seat, a net | network etc. which consist of copper, nickel, stainless steel, titanium, etc .; Sheets, nets and the like made of carbon fibers; Polymer substrates coated with conductive metals; and the like.

Examples of the polymer substrate include polyethylene terephthalate, polyimide, polytetrafluoroethylene, polyethylene naphthalate, polypropylene, polyethylene, polyester, polyvinylidene fluoride, polysulfone, copolymers thereof, and the like. The base material formed from 1 type, or 2 or more types can be used.

In addition, a positive electrode can be formed by crimping | compressing and compressing the positive electrode active material mentioned later in pellet form, without using an electrical power collector.

As the cathode active material, a solid solution represented by Chemical Formula 1 may be used.

[Formula 1]

xLi ₂ MnO ₃ (1-x) LiMO ₂

In Formula 1, 0.1 ≦ x ≦ 0.6. When x is used as the positive electrode active material in the solid solution, it is possible to implement a high capacity lithium secondary battery and at the same time increase the primary particle size of the solid solution, thereby improving the output characteristics of the lithium secondary battery.

In Formula 1, M may include at least one metal selected from Co, Mn, and Ni. Specifically, the metal composite compound represented by the following formula (2) can be used.

[Formula 2]

Mn _a Co _b Ni _c

In Formula 2, 0.3 ≦ a ≦ 0.5, 0.05 ≦ b ≦ 0.3, and 0.3 ≦ c ≦ 0.55, and a + b + c = 1. When using a solid solution having a, b and c in the above range as the positive electrode active material, the lithium secondary battery of high capacity can be realized and the primary particle size of the solid solution can be increased, thereby improving output characteristics of the lithium secondary battery. Can be.

As such, by using the solid solution as the cathode active material, a lithium secondary battery having a high capacity can be realized.

The solid solution may be composed of primary particles and secondary particles. The primary particles correspond to the secondary particles in which solid solutions exist in particulate form and such solid solutions aggregate to form aggregates.

The cathode active material may be prepared by the following method.

The solid solution represented by Chemical Formula 1 and at least one selected from a mixture of a precursor and a lithium compound of the solid solution and molybdate salt may be mixed and then fired by mixing the mixture.

The molybdate salt may be used as a sintering accelerator in the production of the positive electrode active material, and when used, the particle size of the primary particles of the solid solution may be greatly increased without lowering battery characteristics such as storage characteristics, output characteristics, and cycle characteristics. .

Specifically, the number average particle diameter of the primary particles of the solid solution may be 0.5 μm or more, specifically 0.5 to 5 μm, and more specifically 0.5 to 3 μm.

The number-average particle diameter of the primary particles of the solid solution is, for example, by observing the obtained cathode active material layer with a scanning electron microscope (SEM) and image-processing SEM photographs of various fields of view, whereby primary particles of the solid solution existing in each image are present. It can obtain from what occupies the number average of the particle diameter of a particle | grain.

As such, the particle diameter of the primary particles of the solid solution can be greatly increased, and thus the electrode density of the positive electrode including the positive electrode active material can be increased to 2.8 g / cc or more. Accordingly, a lithium secondary battery having high capacity may be realized by greatly increasing the capacity per unit volume of the battery.

In addition to the positive electrode active material described above, the positive electrode may include, for example, an additive such as a conductive agent, a binder, a filler, a dispersant, an ion conductive agent, and the like.

Examples of the conductive agent include graphite, carbon black, acetylene black, KETJEN BLACK, carbon fiber, and metal powder. Examples of the binder include polytetrafluoroethylene and poly Vinylidene fluoride, polyethylene, and the like.

The binder, the filler, the dispersant, and the ion conductive agent may be a material generally used.

The negative electrode includes a current collector and a negative electrode active material layer formed on the current collector and including a negative electrode active material.

As the current collector, a foil made of copper, nickel, stainless steel, titanium, or the like can be used.

Examples of the negative electrode active material include graphite-based carbon materials, silicon, tin, silicon alloys, tin alloys, silicon oxides, lithium vanadium oxides, and the like, but in particular, silicon, tin, silicon alloys, tin alloys, and the like. The compound which can alloy with lithium, silicon oxide, lithium vanadium oxide, etc. are mentioned.

The capacity density of the graphite-based carbon material may be 560 to 630 mAh / cm ³ , and the capacity density of the silicon, tin, silicon alloy, tin alloy, silicon oxide, and lithium vanadium oxide may be 850 mAh / cm ^{3 or} more. By using these, the miniaturization and high capacity of a lithium secondary battery can be aimed at.

The said negative electrode active material may be used independently and 2 or more types may be used together.

In addition to the negative electrode active material described above, the negative electrode may include, for example, an additive such as a conductive agent, a binder, a filler, a dispersant, an ion conductive agent, and the like.

As said electrolyte solution, the non-aqueous electrolyte which melt | dissolved lithium salt in the organic solvent, a polymer electrolyte solution, an inorganic solid electrolyte solution, the composite material of a polymer electrolyte solution and an inorganic solid electrolyte solution, etc. are mentioned, for example.

As an organic solvent of the said non-aqueous electrolyte solution, For example, cyclic carbonates, such as ethylene carbonate, propylene carbonate, vinylene carbonate; Chain carbonates such as dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate; γ-lactones such as γ-butyl lactone; Chain ethers such as 1,2-dimethoxy ethane, 1,2-diethoxy ethane and ethoxy methoxy ethane; Cyclic ethers of tetrahydrofuran; Nitriles, such as acetonitrile, etc. are mentioned.

The organic solvents may be used alone or in combination of two or more thereof.

Examples of the lithium salt that is a solute of the nonaqueous electrolyte include LiAsF ₆ , LiBF ₄ , LiPF ₆ , LiAlCl ₄ , LiClO ₄ , LiCF ₃ SO ₃ , LiSbF ₆ , LiSCN, LiCl, LiC ₆ H ₅ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiC ₄ P ₉ SO ₃ , and the like.

The concentration of the lithium salt may be 0.6M to 2.0M, specifically 0.7M to 1.6M. When the concentration of the lithium salt is within the above range may have an appropriate viscosity, it can improve the conductivity of the lithium ion.

As the separator, for example, a porous membrane made of polyolefin such as polypropylene or polyethylene can be used.

In addition, a polyamide layer may be formed on the porous membrane, and the polyamide layer may include an inorganic metal compound.

Hereinafter, the manufacturing method of a lithium secondary battery is demonstrated.

A positive electrode is obtained by forming a positive electrode active material layer on an electrical power collector. Hereinafter, a method of manufacturing the cathode active material constituting the cathode active material layer will be described.

First, the solid solution and molybdate salt represented by Formula 1 may be mixed, or the mixture of the precursor and the lithium compound of the solid solution and the molybdate salt may be mixed.

As a precursor of the said solid solution, the metal hydroxide containing at least 1 metal chosen from Co, Mn, and Ni is mentioned, for example.

The lithium compound can be, for example, and the like Li ₂ CO _3.

The molybdate salt is not particularly limited as long as it is a metal molybdate salt. For example, lithium molybdate (Li ₂ MoO ₄ ) or sodium molybdate (Na ₂ MoO ₄ ) can be used.

By using these compounds, the particle diameter of a solid solution can be grown large, without reducing the characteristic of a battery.

The molybdate salt may be mixed in an amount of 3 to 60 parts by mass with respect to 100 parts by mass of the solid solution or 100 parts by mass of the precursor of the solid solution, and specifically 10 to 30 parts by mass. When the molybdate salt is mixed within the above range, the particle size of the primary particles of the solid solution may be increased, the electrode density of the positive electrode including the positive electrode active material may be increased, and the output characteristics of the battery may also be improved.

Subsequently, the mixture obtained by mixing with the molybdate salt can be calcined.

The firing may be carried out at a temperature of 600 to 1050 ℃, specifically 650 to 1000 ℃. When firing at a temperature within the above range, the particle size of the primary particles of the solid solution can be increased, the electrode density of the positive electrode can be increased, and the output characteristics of the battery can be improved.

The firing time is not particularly limited, but may be, for example, 3 to 12 hours. When firing for a time within the above range, the sintering proceeds to obtain desired particles.

After the firing, the mixture prepared by mixing the molybdate salt may be washed with water to remove the molybdate salt and then dried. Specifically, the drying may be overnight at 80 ° C. to obtain a positive electrode active material containing a solid solution particle having a large particle size.

Subsequently, a mixture of the obtained positive electrode active material and various additives such as a conductive agent, a binder, a filler, a dispersant, and an ionic conductive agent can be added to a solvent such as water or an organic solvent to form a slurry or paste.

The obtained positive electrode active material layer can be formed on the current collector by applying the obtained slurry or paste onto the current collector using a coating method such as a doctor blade method, drying, and then compressing and compressing the resultant with a roll or the like.

The obtained positive electrode may have an electrode density of 2.8 g / cc or more, specifically 3.0 to 3.3 g / cc. When using a positive electrode having an electrode density within the above range it can be implemented a lithium secondary battery having excellent output characteristics.

Thereafter, a negative electrode is prepared. The said negative electrode is obtained by forming a negative electrode active material layer on an electrical power collector.

Specifically, as in the production of the positive electrode, a mixture of the above-described negative electrode active material and various additives such as a conductive agent, a binder, a filler, a dispersant, and an ion conductive agent is added to a solvent such as water or an organic solvent to slurry or paste. Make up.

The obtained slurry or paste is applied onto the current collector using a coating method such as a doctor blade method, dried, and then compressed and compressed with a rolling roll to form a negative electrode active material layer on the current collector.

As the electrolyte solution, a nonaqueous electrolyte solution in which a lithium salt is dissolved in an organic solvent can be used. In this case, the solution which melt | dissolved the said lithium salt in the predetermined density | concentration is prepared in the mixed solvent which mixed the said organic solvent, for example, cyclic carbonate and chain carbonate by a predetermined mixing ratio.

Moreover, when using solid electrolyte solutions, such as a polymer electrolyte solution, an inorganic solid electrolyte solution, a composite material of a polymer electrolyte solution, and an inorganic solid electrolyte solution, these are used as electrolyte solution as it is.

In the case where the nonaqueous electrolyte is used as the electrolyte, the separator is interposed between the positive electrode and the negative electrode obtained as described above, and the electrode group wound through the separator is wound into a shape according to a battery case such as a cylindrical or flat plate, and wound. After accommodating an electrode group to a battery case, a lithium secondary battery can be manufactured by pouring electrolyte solution into the battery case which accommodated this electrode.

In addition, when the solid electrolyte is used as the electrolyte, a lithium secondary battery may be manufactured by stacking a solid electrolyte with an electrode instead of injecting an electrolyte.

Hereinafter, specific embodiments of the present invention will be described. However, the embodiments described below are only intended to illustrate or explain the present invention, and thus the present invention should not be limited thereto.

Example  1 to 10 and Comparative example  1 to 10

As a positive electrode active material, a solid solution represented by the following formula (1) was used.

[Formula 1]

xLi ₂ MnO ₃ (1-x) LiMO ₂

(In Formula 1, 0.2≤x≤0.5, M is a metal composite compound represented by the following formula (2).)

[Formula 2]

Mn _a Co _b Ni _c

(In Formula 2, 0.3≤a≤0.5, 0.1≤b≤0.3 and 0.3≤c≤0.5, and a + b + c = 1.)

The cathode active material was prepared by the following method.

First, in the formulas (1) and (2), x, a, b, and c were mixed with a precursor of a solid solution or solid solution having the composition shown in Table 1 below, and a molybdate salt of the kind shown in Table 1 below. At this time, the molybdate salt was mixed in the addition amount shown in Table 1 with respect to 100 parts by mass of the precursor of the solid solution or solid solution. At this time, in the case of using the precursor of the solid solution, the metal hydroxide containing each element of Ni, Co and Mn and Li ₂ CO ₃ was mixed, and then mixed with the molybdate salt.

Then, the mixture of the obtained solid solution or the precursor of solid solution and molybdate salt was put into the kiln, and it baked at the temperature shown in following Table 1 for 6 hours.

The temperature rise time to the baking temperature shown in following Table 1 was made into all 2.5 hours.

After the firing, the solid solution or the mixture of the precursor of the solid solution and the molybdate salt was taken out of the firing furnace, and washed with water and dried overnight at 80 ° C. to obtain the positive electrode active materials of Examples 1 to 10 and Comparative Examples 1 to 9. The positive electrode active material of Comparative Example 10 is not fired.

Subsequently, N-methyl-2-pyrrolidone was added and pasted to a mixture of 90 mass% of the obtained cathode active material, 5 mass% of acetylene black and 5 mass% of polyvinylidene fluoride (PVdF) to prepare a cathode active material composition. And it was apply | coated to aluminum foil and the positive electrode was produced.

Graphite powder was used as the negative electrode active material, and N-methyl-2-pyrrolidone was added to a mixture of 95% by mass of the graphite powder and 5% by mass of polyvinylidene fluoride (PVDF) to prepare a negative electrode active material composition in paste form. And it was apply | coated to copper foil and the negative electrode was produced.

The non-aqueous electrolyte was inject | poured through the polypropylene separator through the obtained positive electrode and negative electrode, and the sample of the lithium secondary battery of Examples 1-10 and Comparative Examples 1-10 was produced.

As the nonaqueous electrolyte, a nonaqueous electrolyte in which LiPF ₆ was dissolved at a concentration of 1.10 mol / L in a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a ratio of 3: 7 was used.

Evaluation 1: evaluation of the positive electrode active material and the positive electrode

For the samples of the lithium secondary batteries produced in Examples 1 to 10 and Comparative Examples 1 to 10, the number average particle diameter of the primary particles of the solid solution present in the positive electrode active material was measured, and the electrode density of the positive electrode was calculated from the measurement results. It was. The calculated number average particle diameter and the electrode density are shown in Table 1 below.

The number average particle diameter of the primary particle of the said solid solution was obtained by randomly selecting 100 particle | grains from the scanning electron microscope (SEM) image of arbitrary magnification, and calculating the average particle diameter in image analysis software. In addition, the electrode density of the said anode was computed from the coating mass of the coin cell electrode drilled in 15 mm (phi), and the thickness after press.

Through Table 1, it can be seen that in Examples 1 to 10, the number average particle diameter of the primary particles of the solid solution is 0.5 µm or more and the electrode density of the anode is also high, 2.9 g / cc or more. On the other hand, in Comparative Examples 1 and 10 without mixing the molybdate salt, Comparative Example 2 in which the molybdate salt was mixed in a small amount, and Comparative Example 4 calcined at a low temperature, the number average particle diameter of the primary particles of the solid solution is It can be seen that the electrode density is small and the anode is low.

In addition, the state of the solid solution prepared in Example 1 and Comparative Example 1 was observed with a scanning electron microscope (SEM), the results are shown in Figures 1a to 1c.

1A is a SEM photograph of solid solution particles before firing according to Example 1, FIG. 1B is a SEM photograph of solid solution particles after firing according to Example 1, and FIG. 1C is a SEM photograph of solid solution particles after firing according to Comparative Example 1 .

Specifically, FIG. 1A shows a state of solid solution particles before firing, FIG. 1B shows a state of solid solution particles after firing at 1000 ° C. by adding molybdate salt as a sintering accelerator, and FIG. 1C does not add a sintering accelerator. The state of the solid solution particle after baking at 1000 degreeC is shown.

Referring to FIGS. 1A to 1C, in the case of Example 1, the solid solution particles before firing are agglomerates of small primary particles, but the primary particles of the solid solution are largely grown after firing with molybdate salt. Able to know. On the other hand, when baking without adding a sintering accelerator according to the comparative example 1, it turns out that the primary particle of a solid solution does not change and a particle diameter does not increase.

From this, when using the positive electrode active material containing the solid solution calcined using the sintering accelerator, it turns out that the particle diameter of the primary particle of a solid solution increases, and therefore the electrode density of a positive electrode becomes high.

Evaluation 2: evaluation of the lithium secondary battery

After charging the lithium secondary batteries produced in Examples 1 to 10 and Comparative Examples 1 to 10 with a constant current (0.1C) and a constant voltage (4.75V) at 25 ° C, the batteries were discharged at a constant current up to a discharge starting voltage of 2.0V, and thus initially discharged. Dose was measured.

In addition, the capacity per unit volume of the lithium secondary battery was calculated by the product of the initial discharge capacity and the electrode density of the positive electrode calculated above.

The calculated initial discharge capacity is shown in Table 1 and FIG. 2, and the capacity per unit volume is shown in Table 1 below.

Through Table 1, it can be seen that in the case of Examples 1 to 10, the initial discharge capacity is lower and the capacity per unit volume is lower than that of Comparative Examples 1 to 10.

 2 is a graph showing initial discharge capacities of lithium secondary batteries of Example 1 and Comparative Example 1. FIG. Capacity degradation before and after firing can be evaluated from the initial discharge capacity of FIG. 2. In the graph of FIG. 2, the vertical axis represents the cell voltage and the horizontal axis represents the discharge capacity. In FIG. 2, the initial discharge capacity at the time of using the solid solution particle before baking as a positive electrode active material for the comparative reference is also shown.

Referring to FIG. 2, in the case of Example 1 in which molybdate salt was added as a sintering accelerator and fired, the capacity was less deteriorated than in the case of using a solid solution before firing, and in Comparative Example 1 in which the sintering accelerator was not added. It can be seen that the capacity is significantly deteriorated compared with the case where a solid solution before firing is used.

From this, it turns out that when the positive electrode active material containing the solid solution baked using the sintering accelerator is used, the capacity | capacitance deterioration by baking is small and the fall of a battery characteristic can also be suppressed.

Comparative Example 3 in which molybdate salt was mixed in a large amount, Comparative Example 5 calcined at a high temperature, Comparative Example 6 having a small amount of Li in the final structure of the solid solution, Comparative Example 7, having a large amount of Li in the final structure of the solid solution In Comparative Examples 8 and 9, where the amount of Co and Ni is small or large in the final structure of the solid solution, the initial discharge capacity is low and the capacity per unit volume is low. In Comparative Example 5, since the particles were fired at a high temperature, the large-size hardening proceeded more than necessary, and the initial discharge capacity was low due to the lack of Li by evaporation of Li.

x a b c Molybdate Types Molybdate addition amount (mass part) Firing temperature (캜) Number Average Particle Size of Primary Particles (㎛) Electrode Density (g / cc) Initial discharge capacity (mAh / g) Capacity per unit volume (mAh / cc) Comparative Example 1 0.35 0.4 0.2 0.4 - - 1000 0.2 2.6 220 572 Example 1 0.35 0.4 0.2 0.4 Li ₂ MoO ₄ 25 1000 0.8 3.0 250 750 Example 2 0.35 0.4 0.2 0.4 Li ₂ MoO ₄ 25 1000 1.0 3.0 245 735 Example 3 0.35 0.4 0.2 0.4 Na ₂ MoO ₄ 25 1000 0.8 3.0 245 735 Comparative Example 2 0.35 0.4 0.2 0.4 Li ₂ MoO ₄ 3 1000 0.3 2.4 250 600 Example 4 0.35 0.4 0.2 0.4 Li ₂ MoO ₄ 5 1000 0.6 2.9 252 731 Example 5 0.35 0.4 0.2 0.4 Li ₂ MoO ₄ 50 1000 1.0 3.2 240 768 Comparative Example 3 0.35 0.4 0.2 0.4 Li ₂ MoO ₄ 60 1000 2.0 3.2 200 640 Comparative Example 4 0.35 0.4 0.2 0.4 Li ₂ MoO ₄ 25 650 0.2 2.4 255 612 Example 6 0.35 0.4 0.2 0.4 Li ₂ MoO ₄ 25 800 2.5 2.9 255 740 Comparative Example 5 0.35 0.4 0.2 0.4 Li ₂ MoO ₄ 25 1100 1.5 3.1 200 620 Comparative Example 6 0.1 0.4 0.2 0.4 Li ₂ MoO ₄ 25 1000 0.8 3.0 200 600 Example 7 0.2 0.4 0.2 0.4 Li ₂ MoO ₄ 25 1000 0.8 3.0 250 750 Example 8 0.5 0.4 0.2 0.4 Li ₂ MoO ₄ 25 1000 0.8 3.0 250 750 Comparative Example 7 0.6 0.4 0.2 0.4 Li ₂ MoO ₄ 25 1000 0.8 3.0 180 540 Comparative Example 8 0.35 0.4 0.05 0.55 Li ₂ MoO ₄ 25 1000 0.8 3.0 170 510 Example 9 0.35 0.4 0.1 0.5 Li ₂ MoO ₄ 25 1000 0.8 3.0 240 720 Example 10 0.35 0.4 0.3 0.3 Li ₂ MoO ₄ 25 1000 0.8 3.0 245 735 Comparative Example 9 0.35 0.4 0.2 0.4 Li ₂ MoO ₄ 25 1000 0.8 3.0 150 450 Comparative Example 10 0.35 0.4 0.2 0.4 - - - 0.2 2.4 258 619

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, And falls within the scope of the invention.

Claims (10)

To include a solid solution represented by the formula (1),
The solid solution comprises primary particles and secondary particles,
Primary particles of the solid solution have a number average particle diameter of 0.5 μm or more
Cathode active material for lithium secondary battery.
[Formula 1]
xLi ₂ MnO ₃ (1-x) LiMO ₂
(In Formula 1, 0.1≤x≤0.6, M is a metal composite compound represented by the following formula (2).)
(2)
Mn _a Co _b Ni _c
(In Formula 2, 0.3≤a≤0.5, 0.05≤b≤0.3 and 0.3≤c≤0.55, and a + b + c = 1.)
The method of claim 1,
The primary particles of the solid solution have a number average particle diameter of 0.5 to 5 ㎛ positive electrode active material for a lithium secondary battery.
Mixing a molybdate salt with at least one selected from a solid solution represented by Formula 1 and a mixture of a precursor and a lithium compound of the solid solution; And
Calcining the mixture prepared by mixing at a temperature of 650 to 1050 ℃,
The molybdate salt is mixed with 100 parts by mass of the solid solution or 100 parts by mass of the precursor of the solid solution, the method for producing a positive electrode active material for lithium secondary batteries.
[Formula 1]
xLi ₂ MnO ₃ (1-x) LiMO ₂
(In Formula 1, 0.1≤x≤0.6, M is a metal composite compound represented by the following formula (2).)
(2)
Mn _a Co _b Ni _c
(In Formula 2, 0.3≤a≤0.5, 0.05≤b≤0.3 and 0.3≤c≤0.55, and a + b + c = 1.)
The method of claim 3,
The firing is a method of producing a positive electrode active material for a lithium secondary battery is carried out at a temperature of 600 to 1050 ℃.
The method of claim 3,
The molybdate salt is mixed with 100 parts by mass of the solid solution or 100 parts by mass of the precursor of the solid solution, the method for producing a positive electrode active material for lithium secondary batteries.
The method of claim 3,
After the firing step,
The method of manufacturing a cathode active material for a lithium secondary battery further comprises the step of removing the molybdate salt by washing the mixture prepared by mixing the molybdate salt.
The method of claim 3,
The molybdate salt is a method for producing a positive electrode active material for a lithium secondary battery comprising at least one selected from lithium molybdate and sodium molybdate.
The cathode active material of claim 1 or 2
A positive electrode for a lithium secondary battery comprising a.
9. The method of claim 8,
The positive electrode is a lithium secondary battery positive electrode having an electrode density of 2.8 g / cc or more.
An anode of claim 8;
cathode; And
Electrolyte
&Lt; / RTI &gt;

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