JP2005141983A - Layered lithium nickel base composite oxide powder for positive electrode material of lithium secondary battery, its manufacturing method, positive electrode for lithium secondary battery, and lithium secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide layered lithium nickel base composite oxide powder for a positive electrode material providing a lithium secondary battery enhancing capacity, and excellent in charge discharge efficiency, rate characteristics, and output characteristics. <P>SOLUTION: Layered lithium nickel manganese cobalt base composite oxide powder has a bulk density of 1.5-2.0 g/cc, a BET specific surface area of 1.5-5 m<SP>2</SP>/g, and a mean primary particle size of 0.1-0.5 μm. The lithium nickel manganese cobalt based composite oxide powder is manufactured by spraying slurry prepared by dispersing a manganese compound and a cobalt compound in a liquid medium, and then drying the sprayed material, mixing with a lithium compound, and baking a mixture. When the viscosity of the slurry in spray-drying is represented by V(cp), the slurry supply amount by S(g/min), and gas supply amount by G(L/min), the spray-drying is conducted under a condition of 0.4≤G/S≤4 and G/S≤0.0012V, and baking is conducted under oxygen-containing atmosphere at 750-900°C. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a layered lithium nickel manganese cobalt based composite oxide powder used as a lithium secondary battery positive electrode material, a method for producing the same, a positive electrode for a lithium secondary battery using the same, and a lithium secondary battery. . In particular, the present invention provides a layered lithium nickel manganese cobalt-based composite oxide powder for a high-density lithium secondary battery positive electrode material capable of providing a lithium secondary battery with high capacity and high charge / discharge efficiency and excellent rate characteristics, and The present invention relates to a manufacturing method thereof, a positive electrode for a lithium secondary battery using the same, and a lithium secondary battery.

  Lithium secondary batteries are excellent in energy density and output density, and are effective in reducing the size and weight. Therefore, the demand for power supplies for portable devices such as notebook computers, mobile phones, and handy video cameras is growing rapidly. ing. Lithium secondary batteries are also attracting attention as power sources for electric vehicles and power load leveling.

  In a lithium secondary battery, a lithium-manganese composite oxide, a lithium-cobalt composite oxide, a lithium-nickel composite oxide, or a part of the transition metal of these composite oxides is usually used as a positive electrode active material. Lithium-based composite oxides of lithium and transition metals substituted with 1 are used. Lithium secondary batteries using these lithium-based composite oxides all have the advantage of high voltage and output. In addition, lithium composite oxides having various compositions have been proposed. Among them, one preferred is a lithium nickel manganese cobalt composite oxide having a layered structure, and a battery using this as a positive electrode active material is It is said that safety is high.

  Conventionally, as a method for producing a lithium nickel manganese cobalt-based composite oxide having a layered structure, a solid phase mixture composed of a lithium compound, a nickel compound, a manganese compound and a cobalt compound is baked at 850 ° C. in an oxygen atmosphere or in air. Methods have been proposed (Patent Documents 1 and 2).

  However, the lithium nickel manganese cobalt-based composite oxide having a layered structure obtained by the above-described conventional method is based on a production method in which the particle form is not controlled, such as directly mixing and firing the respective raw material compounds, so that the bulk density is difficult to increase. It was in particle form. For this reason, the positive electrode using such a lithium nickel manganese cobalt based composite oxide as an active material has a small capacity density per unit volume.

  On the other hand, there is a spray-drying method as a method for producing particles having a bulk density that tends to increase. In this case, for example, a layered lithium nickel composite oxide powder as a positive electrode material of a lithium secondary battery is obtained by spray drying a raw material slurry containing a lithium raw material, a nickel compound and a transition metal compound, and using the obtained dry particles. Manufactured by firing.

  Conventionally, in the production of lithium nickel-based composite oxide powder by this spray drying method, the viscosity of the raw material slurry is an important factor, and if the viscosity of the raw material slurry is made excessively low in consideration of the sprayability from the spray nozzle. Usually, the viscosity of the raw material slurry was set to 200 to 1000 cp because it is difficult to form spherical particles and the nozzle is easily clogged when the viscosity is too high. Moreover, from the viewpoint of industrial productivity and the meaning of preventing nozzle clogging, the gas supply amount at the time of spray drying is set to a large excess with respect to the normal slurry, and spray drying using the slurry having the viscosity as described above. The ratio G / S (gas-liquid ratio) of the gas supply amount G (L / min) to the slurry supply amount S (g / min) was set to 5 or more gas excess.

  However, the lithium nickel composite oxide powder obtained using such a gas-excessive spray drying condition tends to have a small average particle size of secondary particles formed during spray drying. A powder having a small average secondary particle diameter has a problem that the bulk density is low and the packing density of the positive electrode active material layer cannot be increased. In particular, in the case of lithium nickel manganese cobalt based composite oxide, there is a problem that a material having a small average secondary particle size is easily obtained, the bulk density is low, and the packing density in the positive electrode active material layer is low.

  Therefore, as a result of intensive studies, the present inventor has spray-dried a slurry in which a nickel compound and a metal element compound capable of substituting a part of nickel are dispersed in a liquid medium, and then mixed with a lithium compound, and the mixture is fired. In producing a layered lithium nickel composite oxide powder for a positive electrode material for a lithium secondary battery, the slurry viscosity during spray drying is V (cp), the slurry supply amount is S (g / min), and the gas supply amount is When G (L / min) is set, the gas-liquid ratio G / S is 0.4 ≦ G / S ≦ 4, and the relationship between the slurry viscosity V and the gas-liquid ratio G / S is G / S. By spray drying under the condition of S ≦ 0.0012V, the bulk density is 2.0 g / cc or more, the average primary particle diameter B is 0.1 to 1 μm, and the median diameter A of the secondary particles is 9 to 20 μm. Secondary median diameter A and average primary particle diameter It was found that a layered lithium nickel composite oxide powder for a lithium secondary battery positive electrode material having a ratio A / B with B in the range of 10 to 200 could be obtained, and a patent application was made earlier (Patent Document 3 below). Say "first application.")

The layered lithium nickel-based composite oxide powder for a lithium secondary battery positive electrode material of the prior application has a very high bulk density and exhibits excellent characteristics such as a high battery capacity when applied as a positive electrode material for a lithium secondary battery. . However, since the BET specific surface area of the powder obtained in the example of the lithium nickel composite oxide powder of the prior application is as low as 0.5 to 1 m ² / g, the charge / discharge efficiency and the current rate are very high. For applications such as high-power batteries that require characteristics, the required performance could not be sufficiently satisfied. In order to sufficiently satisfy such charge / discharge efficiency and current rate characteristics while maintaining a high battery capacity, a layered lithium nickel composite oxide for a lithium secondary battery positive electrode material with a suitable balance of bulk density and BET specific surface area Powder was needed.

On the other hand, in order to obtain a high bulk density, dry particles obtained by spray drying are calcined at a high temperature at which sintering between primary particles occurs actively, or dry particles obtained by spray drying are obtained. It is possible to increase the bulk density by adding a sintering aid before firing, but in this case, the growth of primary particles is promoted and the specific surface area is reduced. When lithium nickel manganese cobalt based composite oxide is used, there is a problem that battery performance such as charge / discharge efficiency, rate characteristics, and output characteristics becomes insufficient.
JP-A-8-37007 Japanese Patent Laid-Open No. 5-242891 Japanese Patent Application No. 2003-185175

  In recent years, with the rapid expansion of the application of lithium secondary batteries as power sources for portable devices such as notebook computers, mobile phones, and handy video cameras, there is a need for higher performance of lithium secondary batteries. Increasingly. In particular, it is desired to improve battery performance such as charge / discharge efficiency and rate output characteristics as well as high initial charge / discharge capacity.

  Therefore, the present invention has an appropriate bulk density while having a high specific surface area. Therefore, the packing density per unit volume is large and the capacity can be increased, and the charge / discharge efficiency, rate characteristics and output characteristics are excellent. Layered lithium nickel manganese cobalt based composite oxide powder for a lithium secondary battery positive electrode material capable of providing a rechargeable lithium secondary battery, a method for producing the same, a positive electrode for a lithium secondary battery excellent in battery performance using the same, and lithium An object is to provide a secondary battery.

The layered lithium nickel manganese cobalt-based composite oxide powder for lithium secondary battery positive electrode material of the present invention is a layered lithium nickel manganese cobalt-based lithium secondary battery positive electrode material formed by agglomerating primary particles to form secondary particles. The composite oxide powder has a bulk density of 1.5 to 2.0 g / cc, a BET specific surface area of 1.5 to ⁵ m ² / g, and an average primary particle size of 0.1 μm or more and 0.0. It is characterized by being less than 5 μm.

That is, the present inventor has clarified the following as a result of intensive studies.
(1) Lithium-based composite oxide powder produced by spray drying improves battery performance such as charge / discharge efficiency, rate characteristics, and output characteristics as the specific surface area increases, and the specific surface area depends on the secondary particle size. Without depending on the primary particle size.
(2) When the primary particle size is constant, there is a correlation that the larger the secondary particle size, the higher the bulk density.

  And based on the above knowledge, by optimizing the spray drying conditions, mixing conditions, firing conditions, etc., that is, after devising the conditions at the time of spray drying, the firing atmosphere is selected and the firing temperature is set low. By suppressing the growth of primary particles, the secondary particle size is made relatively large, an appropriate bulk density can be obtained while having a high specific surface area, high capacity, excellent charge / discharge efficiency, rate characteristics and output characteristics. It was found that layered lithium nickel manganese cobalt based composite oxide powder capable of realizing a lithium secondary battery was obtained.

  Since the layered lithium nickel manganese cobalt based composite oxide powder of the present invention has a large specific surface area and an appropriate bulk density, the positive electrode using this as an active material is a battery with initial efficiency, rate characteristics, output characteristics, etc. High capacity is possible due to excellent performance and high packing density per unit volume.

  In the layered lithium nickel manganese cobalt composite oxide powder for a lithium secondary battery positive electrode material of the present invention, the median diameter of the secondary particles is preferably 9 to 20 μm.

The composition of the layered lithium nickel manganese cobalt based composite oxide according to the present invention is preferably represented by the following formula (I).
_{Li 1 + x Ni 1-y} -z-p Mn y Co z M p O 2 ... (I)
(However, 0 ≦ x ≦ 0.20, 0.1 ≦ y ≦ 0.5, 0.05 ≦ z ≦ 0.5, 0 ≦ p ≦ 0.2, 0.2 ≦ y + z + p ≦ 0.8. , M is one or more of Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, and Nb)

  In the present invention, the bulk density of the layered lithium nickel manganese cobalt based composite oxide powder for lithium secondary battery cathode material is about 10 g of layered lithium nickel manganese cobalt based composite oxide powder for lithium secondary battery cathode material. It is the powder packing density (tap density) when tapped 200 times in a 10 ml glass graduated cylinder. The BET specific surface area of the layered lithium nickel manganese cobalt based composite oxide powder for a lithium secondary battery positive electrode material can be measured by a BET method using a nitrogen adsorption method. The BET method is a method of calculating and measuring the specific surface area (BET specific surface area) of a sample by determining the amount of nitrogen monolayer adsorbed on the adsorption isotherm, determining the surface area from the cross-sectional area of the adsorbed nitrogen molecules.

  The average primary particle diameter of the layered lithium nickel manganese cobalt based composite oxide powder for lithium secondary battery positive electrode material, that is, the average primary particle diameter was measured from an SEM image observed at 30,000 times. is there. The median diameter of the secondary particles is measured at a refractive index of 1.24 using a known laser diffraction / scattering particle size distribution measuring apparatus. In the present invention, a 0.1 wt% sodium hexametaphosphate aqueous solution was used as a dispersion medium used in the measurement, and the measurement was performed after ultrasonic dispersion for 5 minutes.

The method for producing the layered lithium nickel manganese cobalt based composite oxide powder for a lithium secondary battery positive electrode material of the present invention is the layered lithium nickel manganese cobalt based composite oxide powder for a lithium secondary battery positive electrode material of the present invention. Is a method of manufacturing the above-described method, and includes the following steps (1) to (3).
(1) A step of obtaining a dried product by spray-drying a slurry in which a nickel compound, a manganese compound, and a cobalt compound are dispersed in a liquid medium, wherein the slurry viscosity at the time of spray-drying is V (cp), and the amount of slurry supplied Is S (g / min) and the gas supply rate is G (L / min), the gas-liquid ratio G / S is 0.4 ≦ G / S ≦ 4, and the slurry viscosity V and gas Spray drying step of performing spray drying under the condition that the ratio G / S is G / S ≦ 0.0012V (2) Mixing the spray dried product with a lithium compound to form a calcined precursor mixture Step (3) A firing step of firing the firing precursor mixture at 750 to 900 ° C. in an oxygen-containing atmosphere.

  In this method, lithium hydroxide is preferred as the lithium compound.

  In the present invention, the viscosity of the slurry can be measured using a known BM viscometer. The BM viscometer is a measurement method that employs a method of rotating a predetermined metal rotor in the room temperature atmosphere. The viscosity of the slurry is calculated from the resistance force (twisting force) applied to the rotating shaft when the rotor is rotated with the rotor immersed in the slurry. However, the room temperature atmosphere refers to an environment at a laboratory level which is normally considered to have a temperature of 10 to 35 ° C. and a relative humidity of 20 to 80% RH.

  The positive electrode for a lithium secondary battery of the present invention comprises a positive electrode active material layer containing a layered lithium nickel manganese cobalt based composite oxide powder for a lithium secondary battery positive electrode material of the present invention and a binder on a current collector. It is characterized by having.

  The lithium secondary battery of the present invention is a lithium secondary battery comprising a negative electrode capable of inserting and extracting lithium, a nonaqueous electrolyte containing a lithium salt, and a positive electrode capable of inserting and extracting lithium. As a feature, the positive electrode for a lithium secondary battery of the present invention is used.

  According to the present invention, the layered lithium nickel manganese cobalt based composite oxide powder for a positive electrode material for a high-density lithium secondary battery having an appropriate bulk density and a high specific surface area enables high capacity, high efficiency, and rate A lithium secondary battery excellent in battery performance such as characteristics is provided.

Hereinafter, embodiments of the present invention will be described in detail.
First, the layered lithium nickel manganese cobalt-based composite oxide powder for a lithium secondary battery positive electrode material of the present invention will be described.

The layered lithium nickel manganese cobalt-based composite oxide powder for lithium secondary battery positive electrode material of the present invention is a layered lithium nickel manganese cobalt-based lithium secondary battery positive electrode material formed by agglomerating primary particles to form secondary particles. The composite oxide powder has a bulk density of 1.5 to 2.0 g / cc, a BET specific surface area of 1.5 to ⁵ m ² / g, and an average primary particle size of 0.1 μm or more and 0.0. It is less than 5 μm.

  The bulk density of the layered lithium nickel manganese cobalt based composite oxide powder of the present invention is 1.5 g / cc or more, preferably 1.6 g / cc or more, 2.0 g / cc or less, preferably 1.9 g / cc. It is as follows. If the bulk density of the layered lithium nickel manganese cobalt based composite oxide powder of the present invention is below the above lower limit, the powder filling property and electrode preparation will be adversely affected, and the positive electrode using this as the active material has a capacity per unit volume. If the density becomes too small and the above upper limit is exceeded, the BET specific surface area may be reduced, which may be less than the above range.

Moreover, the layered lithium nickel manganese cobalt based composite oxide powder of the present invention has a BET specific surface area of 1.5 to ⁵ m ² / g and a high specific surface area. Below this lower limit, the charge / discharge efficiency, rate characteristics, and output characteristics are likely to deteriorate.If the upper limit is exceeded, the high-temperature cycle life, storage characteristics, and safety deteriorate, and problems arise in coating properties when forming the positive electrode active material layer. Cheap. Therefore, the BET specific surface area is 1.5 m ² / g or more, preferably 2 m ² / g or more and 5 m ² / g or less, preferably 3.5 m ² / g or less.

  Furthermore, the layered lithium nickel manganese cobalt composite oxide powder of the present invention has an average primary particle size of 0.1 μm or more and less than 0.5 μm. If the average primary particle diameter is below the lower limit, crystals may be underdeveloped, which may cause problems such as inferior charge / discharge reversibility, and if the upper limit is exceeded, spherical secondary particles are difficult to form. This is not preferable because it adversely affects body filling properties and the specific surface area is greatly reduced, which increases the possibility of battery performance such as rate characteristics and output characteristics being lowered. Therefore, the average primary particle diameter is 0.1 μm or more, preferably 0.15 μm or more, and less than 0.5 μm, preferably 0.4 μm or less.

  The layered lithium nickel manganese cobalt composite oxide powder of the present invention preferably has a median diameter of secondary particles in the range of 9 to 20 μm.

  Further, if the median diameter of the secondary particles of the layered lithium nickel manganese cobalt based composite oxide powder of the present invention deviates from the above range, either the bulk density or the BET specific surface area defined in the present invention may not be satisfied. This is not preferable. Accordingly, the median diameter of the secondary particles is preferably 9 μm or more, more preferably 10 μm or more, preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 13 μm or less.

The composition of the lithium nickel manganese cobalt-based composite oxide having a layered structure according to the present invention is not particularly limited and can be widely applied to various layered lithium nickel manganese cobalt-based composite oxides. ) Is preferred.
_{Li 1 + x Ni 1-y} -z-p Mn y Co z M p O 2 ... (I)
(However, 0 ≦ x ≦ 0.20, 0.1 ≦ y ≦ 0.5, 0.05 ≦ z ≦ 0.5, 0 ≦ p ≦ 0.2, 0.2 ≦ y + z + p ≦ 0.8. M is one or more of Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, and Nb)

  In the above formula (I), the lower limit of x is usually 0 or more, preferably 0.01 or more, more preferably 0.02 or more, and the upper limit is usually 0.20 or less, preferably 0.15 or less. More preferably, it is 0.10 or less. If the lower limit is not reached, unreacted substances may remain or the crystal structure tends to be unstable, and if the upper limit is exceeded, a heterogeneous phase is likely to be generated or the transition metal site may be substituted. There is a risk of battery performance degradation.

  Moreover, the lower limit of y is usually 0.1 or more, preferably 0.2 or more, and the upper limit is usually 0.5 or less, preferably 0.4 or less. If y is less than this lower limit, it may be difficult to make use of the merit of safety as a battery, and if it exceeds the upper limit, synthesis of a single phase may be difficult.

  The lower limit of z is usually 0.05 or more, preferably 0.2 or more, and the upper limit is usually 0.5 or less, preferably 0.4 or less. If z is less than this lower limit, synthesis may be difficult or battery performance may be greatly reduced. If z exceeds the lower limit, there is a risk that battery safety and cost may be disadvantageous.

  The lower limit of p is usually 0 or more, preferably 0.01 or more, and the upper limit is usually 0.2 or less, preferably 0.1 or less. When p is larger than this upper limit, the capacity when used as an electrode for a battery may be reduced, or it may be difficult to obtain the powder properties of the present invention.

  Further, the lower limit of y + z + p is usually 0.2 or more, preferably 0.3 or more, and the upper limit is usually 0.8 or less, preferably 0.7 or less. If y + z + p is less than this lower limit, synthesis may be difficult, or chemical stability may be deteriorated due to absorption of carbon dioxide gas during storage. There is a risk that the capacity will be significantly reduced.

  The substitution element M is at least one of Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, and Nb, but those having the property of suppressing the growth of primary particles are particularly preferable. From the viewpoint of suppressing growth, M is preferably Al or Nb.

  In particular, the layered lithium nickel manganese cobalt based composite oxide powder for a lithium secondary battery positive electrode material of the present invention is preferably produced by a spray drying method, and in particular, the following shape obtained by the spray drying method: By having the characteristics, even higher performance can be obtained.

  That is, in cross-sectional SEM observation, it is preferable that the orientation of primary particles forming secondary particles is low. This indicates that the primary particle crystals are randomly aggregated to form secondary particles, and the secondary particles have substantially no crystal anisotropy. As a result, in the secondary particles, the expansion and contraction of the crystals accompanying the insertion / release of lithium ions is relieved, the battery characteristics are excellent in cycle reversibility, and in combination with the effects of the substance provision of the present invention, it becomes a conventional product. In addition to further higher density, various battery characteristics have improved performance in a well-balanced manner.

  The method for producing the layered lithium nickel manganese cobalt composite oxide powder for a lithium secondary battery positive electrode material of the present invention is not particularly limited, but preferably, the layered lithium nickel for the lithium secondary battery positive electrode material of the present invention. According to the manufacturing method of the manganese cobalt complex oxide powder, it is manufactured as follows.

In the production method of the present invention, layered lithium nickel manganese for positive electrode material for high-density lithium secondary batteries having a high specific surface area while having an appropriate bulk density by devising the following points as a production process: Realization of cobalt-based composite oxide powder was made possible.
(1) A step of obtaining a dried product by spray-drying a slurry in which a nickel compound, a manganese compound, and a cobalt compound are dispersed in a liquid medium, wherein the slurry viscosity at the time of spray-drying is V (cp), and the amount of slurry supplied Is S (g / min) and the gas supply rate is G (L / min), the gas-liquid ratio G / S is 0.4 ≦ G / S ≦ 4, and the slurry viscosity V and gas Spray drying step of performing spray drying under the condition that the ratio G / S is G / S ≦ 0.0012V (2) Mixing the spray dried product with a lithium compound to form a calcined precursor mixture Step (3) A firing step of firing the firing precursor mixture at 750 to 900 ° C. in an oxygen-containing atmosphere.

  Below, each said manufacturing process is demonstrated in order.

(1) Spray drying step A slurry in which at least a nickel compound, a manganese compound, and a cobalt compound are dispersed in a liquid medium is spray dried, mixed with a lithium compound, and the mixture is fired to form a layered lithium nickel manganese cobalt-based composite oxide. In producing a product powder, when the slurry viscosity during spray drying is V (cp), the slurry supply amount is S (g / min), and the gas supply amount is G (L / min), the gas-liquid ratio G / Spray drying is performed under the condition that S is 0.4 ≦ G / S ≦ 4 and the relationship between the slurry viscosity V and the gas-liquid ratio G / S is G / S ≦ 0.0012V.

  If the gas-liquid ratio G / S is lower than the lower limit, the drying property is likely to be reduced or the nozzle is easily clogged, and if the upper limit is exceeded, it is necessary to use a high-viscosity slurry to obtain the particle properties defined in the present invention. It tends to cause nozzle clogging. Therefore, the gas-liquid ratio G / S is 0.4 or more, preferably 0.5 or more and 4 or less, preferably 2 or less, more preferably 1.5 or less.

  When the relationship between the slurry viscosity V (cp) and the gas / liquid ratio G / S is G / S> 0.0012V, the gas / liquid ratio is too high with respect to the slurry viscosity, and the gas / liquid ratio is set low. The growth of the primary particle diameter is suppressed to increase the specific surface area, and the secondary particle diameter is relatively increased to obtain an appropriate bulk density. Therefore, G / S ≦ 0.0012V.

Thus, in the method of the present invention, the gas-liquid ratio G / S is 0.4 ≦ G / S ≦ 4, and the relationship between the slurry viscosity V (cp) and the gas-liquid ratio G / S is G / S ≦ 0.0012V
Spray drying is performed under the following conditions. This spray drying condition is a hatched area in the graph shown in FIG. 1 where the horizontal axis is V and the vertical axis is G / S. In this hatched region, the lower right region, that is, the slurry viscosity V is high, the gas-liquid ratio G / S is small, and the smaller the α is, the smaller the secondary particle of the obtained powder. As the median diameter increases, the bulk density tends to increase.

  In the spray-drying conditions employed in the present invention, the lower limit of α in G / S = αV is in balance with other conditions and cannot be generally limited, and the median diameter of secondary particles is preferably It is appropriately set so that a powder of 20 μm or less, more preferably 15 μm or less is obtained. From the viewpoint of operability and the like, this α is preferably 0.0004 or more and 0.0010 or less.

  In the present invention, if the viscosity V (cp) of the slurry used for spray drying is too low, it may be difficult to form spherical particles, and if it is too high, the supply pump may fail or the nozzle may be blocked. Accordingly, the slurry viscosity V (cp) is preferably 350 cp or more, particularly 500 cp or more and 3000 cp or less, particularly 1500 cp or less, particularly 1200 cp or less.

  The slurry supply amount S and the gas supply amount G are appropriately set depending on the viscosity of the slurry to be used for spray drying, the specifications of the spray drying device to be used, and the like, and cannot be generally specified. The lower limit is usually 10 or more, preferably 20 or more, and the upper limit is usually 45 or less, preferably 40 or less. If the lower limit is not reached, productivity may be hindered. If the upper limit is exceeded, drying may be difficult. The lower limit of the gas supply amount G (L / min) is usually 20 or more, preferably 25 or more, and the upper limit is usually 45 or less, preferably 40 or less. If the lower limit is not reached, the drying property is lowered or the nozzle is likely to be blocked, and if the upper limit is exceeded, secondary particles may not be formed easily.

  In the method of the present invention, the above-mentioned gas-liquid ratio G / S and the relational expression of the gas-liquid ratio G / S and the slurry viscosity V are satisfied, preferably the above-mentioned slurry viscosity, slurry supply amount, and gas supply amount Spray drying may be performed within the above range, and other conditions are appropriately determined according to the type of apparatus to be used, but it is preferable to select the following conditions.

  That is, the spray drying of the slurry is usually performed at a temperature of 50 ° C. or higher, preferably 70 ° C. or higher, and usually 300 ° C. or lower, preferably 250 ° C. or lower. When this temperature is too high, the obtained granulated particles may have a lot of hollow structures, and the powder packing density tends to decrease. On the other hand, if it is too low, problems such as powder sticking and blockage due to moisture condensation at the powder outlet may occur.

  Further, the gas flow flowing out from the spray nozzle is preferably jetted at a gas linear velocity of usually 100 m / sec or more, preferably 200 m / sec or more. If the gas linear velocity is too low, it is difficult to form appropriate droplets. However, since a too high linear velocity is difficult to obtain, the normal injection speed is 1000 m / sec or less.

Of the raw material compounds used in the preparation of the slurry for producing the layered lithium nickel manganese cobalt based composite oxide powder by the method of the present invention, the nickel compounds include Ni (OH) ₂ , NiO, NiOOH, NiCO. ₃・ 2Ni (OH) ₂・ 4H ₂ O, NiC ₂ O ₄・ 2H ₂ O, Ni (NO ₃ ) ₂・ 6H ₂ O, NiSO ₄ , NiSO ₄・ 6H ₂ O, fatty acid nickel, nickel halide, etc. Can be mentioned. Among these, Ni (OH) ₂ , NiO, NiOOH, NiCO ₃ .2Ni (OH) ₂ that does not contain nitrogen atoms or sulfur atoms in that no harmful substances such as NO _x and SO _x are generated during the firing treatment. Nickel compounds such as 4H ₂ O and NiC ₂ O ₄ .2H ₂ O are preferred. Further, Ni (OH) ₂ , NiO, and NiOOH are particularly preferable from the viewpoint of being available as an industrial raw material at a low cost and having a high reactivity. These nickel compounds may be used individually by 1 type, and may use 2 or more types together.

As manganese compounds, manganese oxides such as Mn ₂ O ₃ , MnO ₂ , Mn ₃ O ₄ , MnCO ₃ , Mn (NO ₃ ) ₂ , MnSO ₄ , manganese acetate, manganese dicarboxylate, manganese citrate, manganese fatty acid And manganese salts such as oxyhydroxide, manganese chloride and the like. Among these manganese compounds, MnO ₂ , Mn ₂ O ₃ , and Mn ₃ O ₄ do not generate NO _X, SO _X , CO _{2, and} other gases during the firing process, and can be obtained at low cost as industrial raw materials. Therefore, it is preferable. These manganese compounds may be used individually by 1 type, and may use 2 or more types together.

Cobalt compounds include Co (OH) ₂ , CoO, Co ₂ O ₃ , Co ₃ O ₄ , Co (OCOCH ₃ ) ₂ .4H ₂ O, CoCl ₂ , Co (NO ₃ ) ₂ .6H ₂ O, Examples thereof include Co (SO ₄ ) ₂ · 7H ₂ O. Among them, Co (OH) ₂ , CoO, Co ₂ O ₃ , and Co ₃ O ₄ are preferable in terms of not generating harmful substances such as NO _X and SO _X during the firing process, and more preferably industrially inexpensive. Co (OH) ₂ in terms of availability and high reactivity. These cobalt compounds may be used individually by 1 type, and may use 2 or more types together.

  In addition, as a substitute element source represented by M in the formula (I) (hereinafter sometimes referred to as “substituted metal compound”), substituted metal oxyhydroxides, oxides, hydroxides, halides In addition, inorganic acid salts such as carbonates, nitrates and sulfates, monocarboxylic acid salts such as acetates and oxalates, and organic acid salts such as dicarboxylates and fatty acid salts can be used.

  As the dispersion medium used for preparing the slurry, various organic solvents and aqueous solvents can be used, but water is preferred. The total weight ratio of the nickel compound and other raw material compounds to the weight of the whole slurry is 10% by weight or more, particularly 12.5% by weight or more, and 50% by weight or less, particularly 35% by weight, within the above-mentioned slurry viscosity range. The following is preferable. When this weight ratio is less than the above range, since the slurry concentration is extremely dilute, the spherical particles generated by spray drying become unnecessarily small or easily broken. When this weight ratio exceeds the above range, it becomes difficult to maintain the uniformity of the slurry.

  The average particle size of the solids in the slurry is usually 2 μm or less, preferably 1 μm or less, and particularly preferably 0.5 μm or less. When the average particle size of the solid matter in the slurry is too large, not only the reactivity in the firing step is lowered, but also the sphericity is lowered and the final powder filling density tends to be lowered. However, making particles smaller than necessary leads to an increase in pulverization cost, so that the average particle size of the solid is usually 0.01 μm or more, preferably 0.05 μm or more, and more preferably 0.1 μm or more.

  As a method for controlling the average particle size of the solid matter in the slurry, the raw material compound is preliminarily dry pulverized by a ball mill, a jet mill, etc., and this is dispersed in a dispersion medium by stirring, etc., the raw material compound is stirred in a dispersion medium, etc. And a method of performing wet pulverization using a medium stirring pulverizer, etc. after dispersion, and a method of performing wet pulverization using a medium stirring pulverizer after dispersing the raw material compound in a dispersion medium. It is preferable to use it.

  Air, nitrogen, or the like can be used as a gas to be supplied when the slurry is spray-dried, but usually air is used. These are preferably used under pressure.

(2) Mixing step As a lithium compound mixed with the granulated particles obtained in the spray drying step of (1), Li ₂ CO ₃ , LiNO ₃ , LiNO ₂ , LiOH, LiOH · H ₂ O, LiH, LiF, Examples include LiCl, LiBr, LiI, CH ₃ COOLi, Li ₂ O, Li ₂ SO ₄ , Li acetate, Li dicarboxylate, Li citrate, fatty acid Li, alkyl lithium, lithium halide, and the like. Preferred among these lithium compounds in that it does not generate harmful substances such as NO _X and SO _X during the firing process, a lithium compound containing no nitrogen atom and a sulfur atom, LiOH, LiOH · H ₂ O Is preferred. These lithium compounds may be used alone or in combination of two or more.

  As a particle size of such a lithium compound, an average particle size is usually 500 μm or less, preferably 100 μm or less, in order to improve the mixing property with a dried product obtained by spray drying and to improve battery performance. More preferably, it is 50 micrometers or less, Most preferably, it is 20 micrometers or less. On the other hand, those having a too small particle size have an average particle size of usually 0.01 μm or more, preferably 0.1 μm or more, more preferably 0.2 μm or more, and most preferably 0 because of low stability in the atmosphere. .5 μm or more.

  Although there is no restriction | limiting in particular in the mixing method of the lithium compound to spray-dried particle, It is preferable to use the powder mixing apparatus generally used for industrial use. The atmosphere in the system to be mixed is preferably an inert gas atmosphere in order to prevent carbon dioxide absorption in the air.

(3) Firing step The mixed powder obtained in the mixing step (2) is then fired. Although this firing condition depends on the raw material composition, as a tendency, if the firing temperature is too high, primary particles grow too much, and conversely if too low, the bulk density is too small and the specific surface area becomes too large. The firing temperature varies depending on the type of lithium compound and other metal compounds used as raw materials, but is usually 750 ° C. or higher, preferably 775 ° C. or higher, and usually 900 ° C. or lower, preferably 875 ° C. or lower. is there.

  Although the firing time varies depending on the temperature, it is usually 30 minutes or more and 50 hours or less in the above-mentioned temperature range. If the firing time is too short, it becomes difficult to obtain a layered lithium nickel manganese cobalt based composite oxide powder having good crystallinity, and it is not practical to be too long. If the firing time is too long, crushing becomes necessary after that, or crushing becomes difficult. Therefore, it is preferably 25 hours or less, more preferably 20 hours or less.

  The atmosphere during firing can be an oxygen-containing gas atmosphere such as air, or an inert gas atmosphere such as nitrogen or argon, depending on the composition and structure of the compound to be produced. An oxygen-containing gas atmosphere is preferred in order to prevent oxygen deficiency therein.

  By the manufacturing method as described above, a layered lithium nickel manganese cobalt based composite oxide powder for a high density lithium secondary battery positive electrode material having a high specific surface area while having an appropriate bulk density can be realized.

  Next, the positive electrode for a lithium secondary battery of the present invention will be described.

  The positive electrode for a lithium secondary battery of the present invention is formed by forming a positive electrode active material layer containing a layered lithium nickel manganese cobalt based composite oxide powder for a lithium secondary battery positive electrode material of the present invention and a binder on a current collector. It is made.

  The positive electrode active material layer is usually formed by mixing a positive electrode material, a binder, and a conductive material and a thickener, which are used if necessary, in a dry form into a sheet shape, and then pressing the positive electrode current collector on the positive electrode current collector. Alternatively, these materials are dissolved or dispersed in a liquid medium to form a slurry, which is applied to the positive electrode current collector and dried.

  As the material for the positive electrode current collector, metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum, and carbon materials such as carbon cloth and carbon paper are usually used. Of these, metal materials are preferable, and aluminum is particularly preferable. As for the shape, in the case of a metal material, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punch metal, a foam metal, etc., and in the case of a carbon material, a carbon plate, a carbon thin film, a carbon cylinder Etc. Among these, metal thin films are preferable because they are currently used in industrialized products. In addition, you may form a thin film suitably in mesh shape.

  When a thin film is used as the positive electrode current collector, its thickness is arbitrary, but it is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and usually 100 mm or less, preferably 1 mm or less, more preferably 50 μm or less. The range of is preferable. If the thickness is thinner than the above range, the strength required for the current collector may be insufficient. On the other hand, if it is thicker than the above range, the handleability may be impaired.

  The binder used in the production of the positive electrode active material layer is not particularly limited, and in the case of a coating method, any material that is stable with respect to the liquid medium used during electrode production may be used. Specific examples include polyethylene, Resin polymers such as polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, nitrocellulose, SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluorine rubber, isoprene rubber, butadiene rubber, ethylene・ Rubber polymers such as propylene rubber, styrene / butadiene / styrene block copolymer and hydrogenated products thereof, EPDM (ethylene-propylene-diene terpolymer), styrene / ethylene / butadiene / ethylene copolymer, Styrene / isoprene styrene bromide Copolymer and its hydrogenated thermoplastic elastomeric polymer, syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer, etc. Fluorine polymers such as soft resinous polymers, polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymers, ion conductivity of alkali metal ions (especially lithium ions) And a polymer composition having the same. In addition, these substances may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

  The ratio of the binder in the positive electrode active material layer is usually 0.1% by weight or more, preferably 1% by weight or more, more preferably 5% by weight or more, and usually 80% by weight or less, preferably 60% by weight or less. More preferably, it is 40% by weight or less, and most preferably 10% by weight or less. If the proportion of the binder is too low, the positive electrode active material cannot be sufficiently retained, and the mechanical strength of the positive electrode may be insufficient, and the battery performance such as cycle characteristics may be deteriorated. There is a possibility that it may lead to a decrease in capacity and conductivity.

  The positive electrode active material layer usually contains a conductive material in order to increase conductivity. There are no particular restrictions on the type, but specific examples include metal materials such as copper and nickel, graphite such as natural graphite and artificial graphite, carbon black such as acetylene black, and amorphous carbon such as needle coke. And carbon materials. In addition, these substances may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios. The proportion of the conductive material in the positive electrode active material layer is usually 0.01% by weight or more, preferably 0.1% by weight or more, more preferably 1% by weight or more, and usually 50% by weight or less, preferably 30%. % By weight or less, more preferably 15% by weight or less. If the proportion of the conductive material is too low, the conductivity may be insufficient, and conversely if it is too high, the battery capacity may be reduced.

  As a liquid medium for forming a slurry, a layered lithium nickel manganese cobalt composite oxide powder as a positive electrode material, a binder, and a conductive material and a thickener used as necessary are dissolved or dispersed. The solvent is not particularly limited as long as it can be used, and either an aqueous solvent or an organic solvent may be used. Examples of the aqueous solvent include water and alcohol. Examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N , N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran (THF), toluene, acetone, dimethyl ether, dimethylacetamide, hexamethylphosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, etc. be able to. In particular, when an aqueous solvent is used, a dispersant is added together with the thickener, and a slurry such as SBR is slurried. In addition, these solvents may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The content of the layered lithium nickel manganese cobalt composite oxide powder of the present invention as the positive electrode material in the positive electrode active material layer is usually 10% by weight or more, preferably 30% by weight or more, more preferably 50% by weight or more. In general, it is 99.9% by weight or less, preferably 99% by weight or less. If the proportion of the layered lithium nickel manganese cobalt composite oxide powder in the positive electrode active material layer is too large, the strength of the positive electrode tends to be insufficient, and if it is too small, the capacity may be insufficient.

  The thickness of the positive electrode active material layer is usually about 10 to 200 μm.

  The positive electrode active material layer obtained by coating and drying is preferably consolidated by a roller press or the like in order to increase the packing density of the positive electrode active material.

  Next, the lithium secondary battery of the present invention will be described.

  The lithium secondary battery of the present invention includes the above-described positive electrode for a lithium secondary battery of the present invention capable of occluding and releasing lithium, a negative electrode capable of occluding and releasing lithium, and a non-aqueous electrolyte using a lithium salt as an electrolytic salt, Is provided. Further, a separator for holding a nonaqueous electrolyte may be provided between the positive electrode and the negative electrode. In order to effectively prevent a short circuit due to contact between the positive electrode and the negative electrode, it is desirable to interpose a separator in this way.

  The negative electrode is usually configured by forming a negative electrode active material layer on a negative electrode current collector, similarly to the positive electrode.

  As a material of the negative electrode current collector, a metal material such as copper, nickel, stainless steel, nickel-plated steel, or a carbon material such as carbon cloth or carbon paper is used. Among these, in the case of a metal material, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, etc., and in the case of a carbon material, a carbon plate, a carbon thin film, a carbon cylinder, etc. are mentioned. Among these, metal thin films are preferable because they are currently used in industrialized products. In addition, you may form a thin film suitably in mesh shape. When a metal thin film is used as the negative electrode current collector, the preferred thickness range is the same as the range described above for the positive electrode current collector.

  The negative electrode active material layer includes a negative electrode active material. The negative electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions, but it can usually occlude and release lithium from the viewpoint of high safety. A carbon material is used.

  Although there is no restriction | limiting in particular as a carbon material, Graphite (graphite), such as artificial graphite and natural graphite, and the thermal decomposition thing of organic substance on various thermal decomposition conditions are mentioned. Examples of pyrolysis products of organic matter include coal-based coke, petroleum-based coke, coal-based pitch carbide, petroleum-based pitch carbide, or carbide obtained by oxidizing these pitches, needle coke, pitch coke, phenol resin, crystalline cellulose, etc. And carbon materials obtained by partially graphitizing these, furnace black, acetylene black, pitch-based carbon fibers, and the like. Among them, graphite is preferable, and particularly preferable is artificial graphite, purified natural graphite, or graphite material containing pitch in these graphites, which is manufactured by subjecting easy-graphite pitch obtained from various raw materials to high-temperature heat treatment. Therefore, those subjected to various surface treatments are mainly used. One of these carbon materials may be used alone, or two or more thereof may be used in combination.

  When a graphite material is used as the negative electrode active material, the d value (interlayer distance) of the lattice plane (002 plane) determined by X-ray diffraction by the Gakushin method is usually 0.335 nm or more, and usually 0.34 nm or less, preferably Is preferably 0.337 nm or less.

  Further, the ash content of the graphite material is usually 1% by weight or less, particularly 0.5% by weight or less, and particularly preferably 0.1% by weight or less, based on the weight of the graphite material.

  Further, the crystallite size (Lc) of the graphite material determined by X-ray diffraction by the Gakushin method is usually 30 nm or more, preferably 50 nm or more, and particularly preferably 100 nm or more.

  The median diameter of the graphite material determined by the laser diffraction / scattering method is usually 1 μm or more, especially 3 μm or more, more preferably 5 μm or more, especially 7 μm or more, and usually 100 μm or less, especially 50 μm or less, more preferably 40 μm or less, especially 40 μm or less. It is preferable that it is 30 micrometers or less.

Moreover, the BET specific surface area of the graphite material is usually 0.5 m ² / g or more, preferably 0.7 m ² / g or more, more preferably 1.0 m ² / g or more, and further preferably 1.5 m ² / g. or more, and usually 25.0 m ² / g or less, preferably 20.0 m ² / g, more preferably 15.0 m ² / g or less, still more preferably 10.0 m ² / g or less.

Further, when performing Raman spectroscopy using argon laser light for graphite material, and strength _{I A} of the peak _{P A} is detected in the range of 1580～1620Cm ^-1, is detected in the range of 1350 ^-1 that intensity ratio _I a / _{I B} of the intensity _{I B} of a peak _{P B} is what is preferably 0 to 0.5. Further, the half width of the peak _{P A} is preferably 26cm ^-1 or less, 25 cm ^-1 or less is more preferable. In addition to the above-mentioned various carbon materials, it can also be used as a negative electrode active material of other materials capable of inserting and extracting lithium. Specific examples of the negative electrode active material other than the carbon material include metal oxides such as tin oxide and silicon oxide, and lithium alloys such as lithium alone and lithium aluminum alloys. One of these materials other than the carbon material may be used alone, or two or more thereof may be used in combination. Moreover, you may use in combination with the above-mentioned carbon material.

  As in the case of the positive electrode active material layer, the negative electrode active material layer is usually prepared by slurrying the above-described negative electrode active material, a binder, and optionally a conductive material and a thickener in a liquid medium. It can manufacture by apply | coating to a negative electrode electrical power collector, and drying. As the liquid medium, the binder, the thickener, the conductive material, and the like that form the slurry, the same materials as those described above for the positive electrode active material layer can be used.

  As the electrolyte, for example, known organic electrolytes, polymer solid electrolytes, gel electrolytes, inorganic solid electrolytes, and the like can be used. Among them, organic electrolytes are preferable. The organic electrolytic solution is configured by dissolving a solute (electrolyte) in an organic solvent.

  Here, the type of the organic solvent is not particularly limited. For example, carbonates, ethers, ketones, sulfolane compounds, lactones, nitriles, chlorinated hydrocarbons, ethers, amines, esters, amides. A phosphoric acid ester compound or the like can be used. Typical examples are dimethyl carbonate, diethyl carbonate, propylene carbonate, ethylene carbonate, vinylene carbonate, tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 4-methyl-2-pentanone, 1,2-dimethoxyethane. 1,2-diethoxyethane, γ-butyrolactone, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitrile, benzonitrile, butyronitrile, valeronitrile 1,2-dichloroethane, dimethylformamide, dimethyl sulfoxide, trimethyl phosphate, triethyl phosphate and the like, and these can be used alone or in combination of two or more.

  The organic solvent described above preferably contains a high dielectric constant solvent in order to dissociate the electrolytic salt. Here, the high dielectric constant solvent means a compound having a relative dielectric constant of 20 or more at 25 ° C. Among the high dielectric constant solvents, it is preferable that ethylene carbonate, propylene carbonate, and compounds in which hydrogen atoms thereof are substituted with other elements such as halogen or alkyl groups are contained in the electrolytic solution. The proportion of the high dielectric constant solvent in the electrolytic solution is preferably 20% by weight or more, more preferably 30% by weight or more, and most preferably 40% by weight or more. If the content of the high dielectric constant solvent is less than the above range, desired battery characteristics may not be obtained.

The type of the electrolytic salt is not particularly limited, and any conventionally known solute can be used. Specific examples include LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , LiCl, LiBr, CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, LiN (SO ₂ CF ₃ ) _2. , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiC (SO ₂ CF ₃ ) ₃ , LiN (SO ₃ CF ₃ ) _{2 and the} like. Any one of these electrolytic salts may be used alone, or two or more thereof may be used in any combination and ratio. Further, an additive that forms a good film that enables efficient charge and discharge of lithium ions on the negative electrode surface, such as gas such as CO ₂ , N ₂ O, CO, and SO ₂ , and polysulfide S _x ^2- , at an arbitrary ratio May be added.

  The lithium salt of the electrolytic salt is usually contained in the electrolytic solution so as to have a concentration of 0.5 mol / L to 1.5 mol / L. Even if it is less than 0.5 mol / L or more than 1.5 mol / L, the electrical conductivity may be lowered, and the battery characteristics may be adversely affected. The lower limit is preferably 0.75 mol / L or more and the upper limit is 1.25 mol / L or less.

Even when a polymer solid electrolyte is used, the type thereof is not particularly limited, and any known crystalline / amorphous inorganic substance can be used as the solid electrolyte. Examples of the crystalline inorganic solid electrolyte include LiI, Li ₃ N, Li _{1 + x} J _x Ti _2-x (PO ₄ ) ₃ (J = Al, Sc, Y, La), Li _0.5-3x RE _{0. .5 + x} TiO ₃ (RE = La, Pr, Nd, Sm) and the like. Examples of the amorphous inorganic solid electrolyte include oxide glasses such as 4.9LiI-34.1Li ₂ O-61B ₂ O ₅ and 33.3Li ₂ O-66.7SiO ₂ . Any one of these may be used alone, or two or more may be used in any combination and ratio.

  When the above-described organic electrolyte is used as the electrolyte, a separator is interposed between the positive electrode and the negative electrode in order to prevent a short circuit between the electrodes. The material and shape of the separator are not particularly limited, but those that are stable with respect to the organic electrolyte used, have excellent liquid retention properties, and can reliably prevent short-circuiting between electrodes are preferable. Preferable examples include microporous films, sheets, nonwoven fabrics and the like made of various polymer materials. Specific examples of the polymer material include polyolefin polymers such as nylon, cellulose acetate, nitrocellulose, polysulfone, polyacrylonitrile, polyvinylidene fluoride, polypropylene, polyethylene, and polybutene. In particular, from the viewpoint of chemical and electrochemical stability, which is an important factor for separators, polyolefin polymers are preferable. From the viewpoint of self-occluding temperature, which is one of the purposes of use of separators in batteries, polyethylene is preferred. Is particularly desirable.

  When using a separator made of polyethylene, it is preferable to use ultra-high molecular weight polyethylene from the viewpoint of maintaining high-temperature shape, and the lower limit of the molecular weight is preferably 500,000, more preferably 1,000,000, and most preferably 1,500,000. On the other hand, the upper limit of the molecular weight is preferably 5 million, more preferably 4 million, and most preferably 3 million. This is because if the molecular weight is too large, the fluidity becomes too low, and the pores of the separator may not close when heated.

  The lithium secondary battery of the present invention is manufactured by assembling the above-described positive electrode of the present invention, the negative electrode, an electrolyte, and a separator used as necessary into an appropriate shape. Furthermore, other components such as an outer case can be used as necessary.

  The shape of the lithium secondary battery of the present invention is not particularly limited, and can be appropriately selected from various commonly employed shapes according to the application. Examples of commonly used shapes include a cylinder type with a sheet electrode and separator in a spiral shape, a cylinder type with an inside-out structure combining a pellet electrode and a separator, and a coin type with stacked pellet electrodes and a separator. Can be mentioned. The method for assembling the battery is not particularly limited, and can be appropriately selected from various commonly used methods according to the shape of the target battery.

  The general embodiment of the lithium secondary battery of the present invention has been described above. However, the lithium secondary battery of the present invention is not limited to the above-described embodiment, and various modifications are possible as long as the gist thereof is not exceeded. Can be implemented.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

<Manufacture of layered lithium nickel manganese cobalt based composite oxide powder for positive electrode material of lithium secondary battery>
(Example 1)
Ni (OH) ₂ , Mn ₃ O ₄ , Co (OH) ₂ were used as starting materials, and weighed so that the molar ratio was Ni: Mn: Co = 0.33: 0.33: 0.33, Pure water was added thereto to prepare a slurry. While stirring this slurry, a circulating medium agitation type wet pulverizer (Shinmaru Enterprises Co., Ltd .: Dino Mill KDL)
A type) was pulverized until the average particle size of the solid content in the slurry became 0.19 μm.

Next, this slurry (solid content 15.5% by weight, viscosity 960 cp) was spray-dried using a two-fluid nozzle type spray dryer (Okawara Kako Co., Ltd .: LT-8 type). The spray nozzle used was an external mixing type nozzle, the inner side of the concentric nozzle port was the slurry outlet, the outer side was the pressurized gas outlet, the nozzle outer diameter was 3 mmφ, the slurry outlet diameter was 2.3 mmφ, and pressurization The clearance at the gas outlet was 0.2 mm, and the cross-sectional area was 1.76 mm ² . Air was used as the dry gas at this time, the dry gas introduction amount G was 45 L / min, the gas linear velocity 426 m / sec, and the slurry introduction amount S was 39 g / min (gas-liquid ratio G / S = 1.15). The drying inlet temperature was 90 ° C.

LiOH powder pulverized to an average particle size of 20 μm or less was added to the granulated particle powder obtained by spray drying so that the molar ratio of Li was 1.05 and mixed well. About 13 g of this mixed powder was charged into an alumina crucible and fired at 900 ° C. for 10 hours under an air flow of 9 L / min (temperature increase / decrease rate of 5 ° C./min), so that the composition was Li _1.05 Ni _0.33. A lithium nickel manganese cobalt based composite oxide powder having a layered structure of Mn _0.33 Co _0.33 O ₂ (hereinafter sometimes referred to as “111 composition”) was obtained. The phase was identified by a powder X-ray diffraction pattern.

  About 10 g of this powder was put into a 10 ml glass graduated cylinder, and the bulk density (powder filling density (tap density) when tapped 200 times) was measured. Further, Table 1 shows the BET specific surface area, the median diameter of the secondary particles (ultrasonic dispersion 5 minutes), and the primary particle diameter by SEM observation.

(Example 2)
Using a slurry pulverized to an average solid particle size of 0.15 μm and spray drying with a spray dryer, the slurry solid content is 14.5 wt%, the viscosity is 1120 cp, and the dry gas introduction amount G is 25 L / min. In the same manner as in Example 1, except that the gas linear velocity was 237 m / sec, the slurry introduction amount S was 38 g / min (gas-liquid ratio G / S = 0.66), and the drying inlet temperature was 120 ° C. Lithium nickel manganese cobalt composite oxide powder having a layered structure of 111 composition was obtained by mixing with powder, firing, and crushing.
The physical properties of this powder measured in the same manner as in Example 1 are as shown in Table 1.

(Example 3)
A lithium nickel manganese cobalt composite oxide powder having a layered structure of 111 composition was obtained in the same manner as in Example 2 except that the firing temperature was 850 ° C.
The physical properties of this powder measured in the same manner as in Example 1 are as shown in Table 1.

Example 4
A lithium nickel manganese cobalt composite oxide powder having a layered structure of 111 composition was obtained in the same manner as in Example 2 except that the firing temperature was 800 ° C.
The physical properties of this powder measured in the same manner as in Example 1 are as shown in Table 1.

(Example 5)
In the spray drying of a spray dryer using a slurry of Ni: Mn: Co = 0.45: 0.45: 0.10 (molar ratio) and pulverized to an average solid particle size of 0.15 μm, The content is 12% by weight, the viscosity is 700 cp, the dry gas introduction amount G is 30 L / min, the gas linear velocity 284 m / sec, the slurry introduction amount S is 39 g / min (gas-liquid ratio G / S = 0.77), Except that the drying inlet temperature was 150 ° C. and the firing temperature was 800 ° C., mixing with the pulverized LiOH powder, firing, and pulverization were performed in the same manner as in Example 1, and the composition was Li _1.05 Ni _0.45. A lithium nickel manganese cobalt composite oxide powder having a layered structure of Mn _0.45 Co _0.10 O ₂ (hereinafter sometimes referred to as “992 composition”) was obtained.
The physical properties of this powder measured in the same manner as in Example 1 are as shown in Table 1.

(Comparative Example 1)
A lithium nickel manganese cobalt composite oxide powder having a layered structure of 111 composition was obtained in the same manner as in Example 1 except that the firing temperature was 950 ° C.
The physical properties of this powder measured in the same manner as in Example 1 are as shown in Table 1.

(Comparative Example 2)
A lithium nickel manganese cobalt composite oxide powder having a layered structure of 111 composition was obtained in the same manner as in Example 2 except that the firing temperature was 950 ° C.
The physical properties of this powder measured in the same manner as in Example 1 are as shown in Table 1.

(Comparative Example 3)
In spray drying of a spray dryer, the slurry solid content is 17% by weight, the viscosity is 910 cp, the dry gas introduction amount G is 45 L / min, the gas linear velocity 426 m / sec, and the slurry introduction amount S is 10 g / min (gas-liquid ratio). G / S = 4.50), lithium nickel manganese cobalt composite oxide powder having a layered structure of 111 composition in the same manner as in Example 1 except that the drying inlet temperature was 90 ° C. and the firing temperature was 950 ° C. Got.
The physical properties of this powder measured in the same manner as in Example 1 are as shown in Table 1.

(Comparative Example 4)
In the spray drying of the spray dryer, the slurry solid content is 12% by weight, the viscosity is 250 cp, the dry gas introduction amount G is 30 L / min, the gas linear velocity 284 m / sec, and the slurry introduction amount S is 40 g / min (gas-liquid) Lithium nickel manganese cobalt composite oxide powder having a layered structure of 111 composition in the same manner as in Example 1 except that the ratio G / S = 0.75), the drying inlet temperature was 90 ° C., and the firing temperature was 950 ° C. Got the body.
The physical properties of this powder measured in the same manner as in Example 1 are as shown in Table 1.

(Comparative Example 5)
A lithium nickel manganese cobalt composite oxide powder having a layered structure of 992 composition was obtained in the same manner as in Example 5 except that the firing temperature was 950 ° C.
The physical properties of this powder measured in the same manner as in Example 1 are as shown in Table 1.

<Production and evaluation of battery>
Using the layered lithium nickel manganese cobalt based composite oxide powders produced in Examples 1 to 5 and Comparative Examples 1 to 5, batteries were produced and evaluated by the following methods.

[1] Preparation of positive electrode, confirmation of initial charge / discharge capacity and rate test:
What weighed 75% by weight of the layered lithium nickel manganese cobalt based composite oxide powder produced in Examples 1 to 5 and Comparative Examples 1 to 5, 20% by weight of acetylene black, and 5% by weight of polytetrafluoroethylene powder. Were mixed thoroughly in a mortar, and a thin sheet was punched out using a 9 mmφ punch. At this time, the total weight was adjusted to about 8 mg. This was pressure-bonded to an aluminum expanded metal to obtain a 9 mmφ positive electrode.

A 9 mmφ positive electrode was used as a test electrode, a lithium metal plate as a counter electrode, and 1 mol of LiPF ₆ in a solvent of EC (ethylene carbonate): DMC (dimethyl carbonate): EMC (ethyl methyl carbonate) = 3: 3: 4 (volume ratio). A coin-type cell was assembled using a 25 μm-thick porous polyethylene film as a separator using an electrolytic solution dissolved at / L.

With respect to the obtained coin-type cell, a charge / discharge two-cycle test was conducted at a constant current of 0.2 mA / cm ² with a charge upper limit voltage of 4.3 V and a discharge lower limit voltage of 3.0 V. 10th cycle, constant current charge of 0.5 mA / cm ² , 0.2 mA / cm ² , 0.5 mA / cm ² , 1 mA / cm ² , 3 mA / cm ² , 5 mA / cm ² , 7 mA / cm ² , 9 mA / cm ^2, and were tested at each discharge of 11 mA / cm ^2. Initial discharge capacity at 0.2 mA / cm ² in the first cycle of this time (mA / ^cm 2), and measures the high-rate discharge capacity at the 10th cycle of ^{11mA / cm 2 (mAh / g} ), The results are shown in Table 2.

  From the above results, the following can be understood.

  In Comparative Example 1, although the bulk density is high, the average primary particle size is large and the BET specific surface area is low, so the initial efficiency and the high rate discharge characteristics are not good.

  In Comparative Example 2, the bulk density is very high, but the average primary particle size is large and the BET specific surface area is low, so the initial efficiency and high rate discharge characteristics are not good.

  In Comparative Example 3, the bulk density is 1.5 to 2.0 g / cc, but the primary particles have a large average particle size and a low BET specific surface area, so that the initial efficiency and the high-rate discharge characteristics are not good.

  In Comparative Example 4, the bulk density is 1.5 to 2.0 g / cc, but the primary particles have a large average particle size and a low BET specific surface area, so that the initial efficiency and the high-rate discharge characteristics are not good.

  In Comparative Example 5, the bulk density is 1.5 to 2.0 g / cc, but the primary particles have a large average particle size and a low BET specific surface area, so that the initial efficiency and the high rate discharge characteristics are not good.

In contrast, in Examples 1 to 5, the bulk density is 1.5 to 2.0 g / cc, the BET specific surface area is 1.5 to ⁵ m ² / g, and the average primary particle size is 0.1 μm or more and less than 0.5 μm. Therefore, the initial charge / discharge capacity is high, and the initial efficiency and high-rate discharge characteristics are good.

Accordingly, layered lithium nickel having a bulk density of 1.5 to 2.0 g / cc, a BET specific surface area of 1.5 to ⁵ m ² / g, and an average primary particle size of 0.1 μm or more and less than 0.5 μm. It can be seen that the use of manganese cobalt-based composite oxide powder provides a positive electrode material for a high-density lithium secondary battery and a lithium secondary battery that have high capacity, high efficiency, and excellent rate characteristics.

  The use of the lithium secondary battery provided by the present invention is not particularly limited, and can be used for various known uses. Specific examples include notebook computers, pen input computers, mobile computers, electronic book players, mobile phones, mobile faxes, mobile copy, mobile printers, headphone stereos, video movies, LCD TVs, handy cleaners, portable CDs, minidiscs, and transceivers. Electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, lighting equipment, toys, game machines, watches, strobes, cameras, etc.

It is a graph which shows the relationship between the gas-liquid ratio G / S at the time of spray-drying, and slurry viscosity V (cp).

Claims (7)

It is a layered lithium nickel manganese cobalt based composite oxide powder for a lithium secondary battery positive electrode material formed by agglomerating primary particles to form secondary particles, and has a bulk density of 1.5 to 2.0 g / cc. A layered lithium nickel manganese cobalt based composite for a lithium secondary battery positive electrode material, having a BET specific surface area of 1.5 to ⁵ m ² / g and an average primary particle size of 0.1 μm or more and less than 0.5 μm Oxide powder.   2. The layered lithium nickel manganese cobalt based composite oxide powder for a lithium secondary battery positive electrode material according to claim 1, wherein the median diameter of the secondary particles is 9 to 20 [mu] m. The layered lithium nickel manganese cobalt based composite oxide powder for a lithium secondary battery positive electrode material according to claim 1 or 2, wherein the layered lithium nickel manganese cobalt based composite oxide is represented by the following formula (I): .
_{Li 1 + x Ni 1-y} -z-p Mn y Co z M p O 2 ... (I)
(However, 0 ≦ x ≦ 0.20, 0.1 ≦ y ≦ 0.5, 0.05 ≦ z ≦ 0.5, 0 ≦ p ≦ 0.2, 0.2 ≦ y + z + p ≦ 0.8. , M is one or more of Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, and Nb) A method for producing a layered lithium nickel manganese cobalt based composite oxide powder for a lithium secondary battery positive electrode material according to any one of claims 1 to 3, comprising the following steps (1) to (3): A method for producing a layered lithium nickel manganese cobalt based composite oxide powder for a positive electrode material for a lithium secondary battery, comprising:
(1) A step of obtaining a dried product by spray-drying a slurry in which a nickel compound, a manganese compound, and a cobalt compound are dispersed in a liquid medium, wherein the slurry viscosity at the time of spray-drying is V (cp), and the amount of slurry supplied Is S (g / min) and the gas supply rate is G (L / min), the gas-liquid ratio G / S is 0.4 ≦ G / S ≦ 4, and the slurry viscosity V and gas Spray drying step of performing spray drying under the condition that the ratio G / S is G / S ≦ 0.0012V (2) Mixing the spray dried product with a lithium compound to form a calcined precursor mixture Step (3) A firing step of firing the firing precursor mixture at 750 to 900 ° C. in an oxygen-containing atmosphere.   5. The method for producing a layered lithium nickel manganese cobalt composite oxide powder for a lithium secondary battery positive electrode material according to claim 4, wherein the lithium compound is lithium hydroxide.   A positive electrode active material layer containing a layered lithium nickel manganese cobalt based composite oxide powder for a lithium secondary battery positive electrode material according to any one of claims 1 to 3 and a binder on a current collector. A positive electrode for a lithium secondary battery.   A lithium secondary battery comprising a negative electrode capable of inserting and extracting lithium, a non-aqueous electrolyte containing a lithium salt, and a positive electrode capable of inserting and extracting lithium, wherein the lithium secondary battery according to claim 6 is used as the positive electrode. A lithium secondary battery using a positive electrode for a battery.

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