JP2003272628A - Manufacturing method of lithium transition metal complex oxide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing at low cost a lithium transition metal complex oxide with a high filling density. <P>SOLUTION: With the manufacturing method of the lithium transition metal complex oxide in which slurries having transition metal sources are sprayed and dried and then are mixed with lithium sources to be put under sintering treatment, the above spraying and drying are achieved in following steps: (1) a thin film flow of the slurries is formed between a flat smooth face and the gas flow by supplying the slurries so as to go across the gas flow flowing along the flat smooth face, (2) the above thin film flow is separated from the flat smooth face to form liquid drops, and (3) the liquid drops are dried. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a lithium-transition metal composite oxide and a lithium-ion secondary battery using the same as an active material.

[0002]

_2. Description of the Related Art Lithium-transition metal composite oxides such as layered composite oxides LiCoO ₂ and LiNiO ₂ and spinel-structured LiMn ₂ O ₄ compounds are used as positive electrode active materials for lithium ion secondary batteries. Since the product can obtain a high voltage of 4 V class and has a high energy density, it has already been widely put into practical use or is in the stage of practical use.

On the other hand, the positive electrode active material is usually mixed with a conductive material and a binder to form a positive electrode mixture. The higher the packing density of the positive electrode active material is, the higher the energy density per unit volume is. When the battery of the above is manufactured, a high capacity battery is obtained, and if the battery has the same energy capacity,
There are advantages such as downsizing. In view of this, a method of granulating the positive electrode active material particles into a spherical shape to improve the filling property has been proposed. For example, a method of spray drying a slurry as a raw material, a method of spray pyrolyzing a solution as a raw material, and the like are known.

On the other hand, in the field where charging / discharging at a high current density is required, it is preferable to make the positive electrode mixture layer as thin as possible, and the active material particles used for such applications are
From the viewpoint of the uniformity of the coating film, it becomes necessary to make the particles smaller.

[0005]

However, it is difficult to form particles having a small particle size by spraying. In particular, when the average particle size is in the range of 10 μm or less, there is a problem in the conventional droplet atomizing method (rotary atomizer method, two-fluid nozzle method) in spray drying. That is, in the rotary atomizer method, it is necessary to make the solid content concentration extremely low, and in the two-fluid nozzle method, the nozzle 1
Since the productivity per book is low, the number of nozzles is increased and the device is enlarged, which is not always sufficient in terms of industrially inexpensive production. Further, according to the study by the present inventors, it has been found that the following problems occur when spray drying is carried out in the production of the lithium-transition metal composite oxide. That is, when a lithium source is present in the slurry during spray drying, the water-soluble lithium compound is selectively deposited on the surface, and the shell of the lithium compound is generated on the particle surface, resulting in hollow particles after drying. As a result, a sufficient packing density cannot be obtained.

The present invention provides a method for producing a lithium transition metal composite oxide suitable as a positive electrode active material for a lithium ion secondary battery, and in particular, a method for mass-producing a lithium transition metal composite oxide having a high packing density at low cost. The purpose is to do.

[0007]

Means for Solving the Problems The inventors of the present invention have earnestly studied a cheaper manufacturing method for increasing the bulk density of a lithium-transition metal composite oxide, and as a result, (1) a slurry liquid for spray drying. As a method for forming droplets, a thin film flow of the slurry is formed between the smooth surface and the gas flow by supplying a slurry so as to intersect the gas flow flowing along the smooth surface, and then the thin film flow is formed. It was found that it is effective to combine the method of separating the granulated particles obtained by the spray drying with the method of mixing the raw material and the method of mixing the raw material (2) as the mixing method of the raw materials. Completed the invention.

That is, the gist of the present invention is as follows (1)-
It exists in (14). (1) In a method for producing a lithium-transition metal composite oxide, which comprises spray-drying a slurry containing a transition metal source, mixing the slurry with a lithium source, and subjecting the mixture to a calcination treatment, the spray drying is performed along a smooth surface. By supplying the slurry so as to intersect the flowing gas stream, thereby forming a thin film stream of the slurry between the smooth surface and the gas stream,
A method for producing a lithium-transition metal composite oxide, characterized in that droplets are formed by separating the thin film stream from the smooth surface, and the droplets are dried. (2) The production method according to (1), characterized in that the spray drying is performed under a condition of a dry gas temperature of 50 to 300 ° C. (3) The injection velocity of the gas flow is 100 to 1000 at the linear gas velocity.
The production method according to (1) or (2), which is m / s. (4) The production method according to any one of (1) to (3), wherein the solid particles in the slurry have an average particle size of 2 μm or less. (5) The production method according to any one of (1) to (4), wherein the obtained lithium-transition metal composite oxide has an average particle size of 4 to 50 μm. (6) The manufacturing method according to any one of (1) to (5), wherein the droplets are sprayed in a ring shape. (7) The droplets are sprayed in a substantially horizontal direction, and the sprayed droplets are introduced with a dry gas by downflow (1) to
The manufacturing method according to any one of (6). (8) A slurry, a transition metal source containing at least one transition metal element selected from the group consisting of Mn, Ni, and Co, and Al, Ti, V, Cr, Fe, Cu, Zn, M.
a metal element source containing at least one metal element selected from the group consisting of g, Ga, and Zr (1) to
The manufacturing method according to any one of (7). (9) The metal element source is Al, Ti, V, Cr, Fe, C
selected from oxides, hydroxides, oxyhydroxides, nitrates, sulfates, carbonates, dicarboxylates, fatty acid salts and ammonium salts of elements selected from the group consisting of u, Zn, Mg, Ga and Zr. Is at least one (8)
The manufacturing method described in. (10) The lithium source is Li ₂ CO ₃ , LiNO ₃ , Li
OH, LiOH · H ₂ O, LiI, CH ₃ COOLi, L
i ₂ O, Li dicarboxylic acid, Li citric acid, L fatty acid
The production method according to any one of (1) to (9), which is at least one selected from the group consisting of i, alkyllithium, and lithium halide. (11) The production method according to any one of (1) to (10), in which the lithium-transition metal composite oxide is represented by the following general formula (I).

[0009]

## STR2 ## _{Li x M y O 2 ± δ} (I) ( here, x is the number of 0.4 to 1.2, y is 0.8 to 1.
Number of 1, M is Mn, Ni, Co, Al, Ti, V, C
at least one element selected from the group consisting of r, Fe, Cu, Zn, Mg, Ga, and Zr, and δ is -0.1 to 0.
(12) (12) A coating material containing a mixture of a lithium transition metal composite oxide obtained by the method according to any one of (1) to (11) and a binder, and a solvent, Apply on current collector
A method for producing an electrode, which comprises drying. (13) A lithium secondary battery in which the lithium transition metal composite oxide obtained by the method according to any one of (1) to (11) is used as a positive electrode active material.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The slurry subjected to spray drying has at least one type of transition metal source. As the dispersion medium of the slurry, various organic solvents and aqueous solvents can be used, but water is preferably used. The average particle size of undissolved solids in the slurry is usually 2 μm or less, preferably 1 μm
Hereafter, it is more preferably 0.5 μm or less. If the average particle size of the solid matter in the slurry is too large, the sphericity tends to decrease, and the final powder packing density tends to decrease. This tendency is particularly remarkable when trying to produce granulated particles having an average particle size of 50 μm or less. As a method for controlling the average particle diameter of the solid matter in the slurry, a raw material powder is previously dry-milled by a ball mill, a jet mill or the like, and a method of dispersing this in a dispersion medium, after dispersing the raw material powder in the dispersion medium,
A method of wet pulverization using a medium agitation pulverizer or the like can be mentioned. It should be noted that making the particles smaller than necessary leads to an increase in the cost of pulverization and is not preferable, so the average particle diameter of the solid is usually 0.01 μm or more, preferably 0.05 μm.
Or more, and more preferably 0.1 μm or more.

When a lithium source is present in the slurry,
Although the productivity tends to be relatively low and the packing density of the obtained lithium-transition metal composite oxide tends to be relatively low, a part of the lithium source used as a raw material can be contained in the slurry. As the lithium source in this case,
Li ₂ CO ₃ , LiNO ₃ , LiOH, LiOH.H ₂ O,
LiI, CH ₃ COOLi, Li ₂ O, dicarboxylic acid L
i, Li citrate, fatty acid Li, alkyllithium, lithium halide and the like can be used. Of course, a plurality of types can be used together. However, when a large amount of lithium source is contained in the slurry, the above tendency becomes apparent. Therefore, usually 50% by weight or less of the lithium source used,
Preferably 30% by weight or less, more preferably 10% by weight or less is contained in the slurry. Most preferably, the lithium source is not included in the slurry and the entire amount is used in the mixing with the granulated particles obtained by spray drying.

The transition metal source contained in the slurry for forming the lithium transition metal composite oxide contains various transition metals such as manganese, nickel, cobalt, iron and copper. It preferably contains manganese, nickel or cobalt. Usually, as the transition metal source, a transition metal oxide,
An organic acid salt such as carbonate, nitrate, sulfate, acetic acid, hydroxide, oxyhydroxide or halide is used. Of course, a plurality of these may be used in combination.

In the slurry, Al, Zn and M are further added.
A compound containing an element other than a transition metal source such as g or Ga may be contained. Further, when at least one selected from the group consisting of nickel, cobalt and manganese is used as a main component of the transition metal, a part of the transition metal site in the finally obtained lithium transition metal composite oxide is substituted, etc. For Al, Ti, V, Cr, F
A metal element source containing elements such as e, Cu, Zn, Mg, Ga, and Zr can be contained in the slurry. Specifically, as the metal element source, at least one selected from oxides, hydroxides, oxyhydroxides, nitrates, sulfates, carbonates, dicarboxylates, fatty acid salts and ammonium salts of the above elements can be given. You can

The resulting slurry is subjected to spray drying. In the present invention, (1) by supplying the slurry so as to intersect the gas flow flowing along the smooth surface, a thin film flow of the slurry is provided between the smooth surface and the gas flow. And (2) separating the thin film stream from the smooth surface to form droplets, and (3) drying the droplets.

FIG. 1 is a schematic side view of a nozzle portion of a spray dryer that can be used for spray drying in the present invention (a hatched portion shows a partially cut cross section), and FIG. FIG. 3 is a schematic cross-sectional view showing an enlarged nozzle tip of No. 1 together with a gas flow and a flow of slurry. In the cylindrical nozzle 1, a nozzle tip 3 having a smooth inclined surface 2 is provided in an annular shape around the cylinder. A gas outlet 4 for supplying a high-speed gas flow flowing along the inclined surface 2 through a gas supply pipe 7 is provided at the nozzle tip 3 toward the inclined surface 2. A slurry outlet 5 for supplying the slurry through the slurry supply pipe 8 is provided at the nozzle tip 3 so that the discharged slurry intersects the flow direction of the gas flow discharged along the inclined surface. ing.

As the gas supplied as the gas flow, air, nitrogen or the like can be used, but air is usually used. It is preferable to use these under pressure. The gas flow has a gas linear velocity of usually 100 m / s or more, preferably 200 m / s or more, and more preferably 300 m / s.
It is injected at s or more. If it is too small, it becomes difficult to form appropriate droplets. However, since it is difficult to obtain a too high linear velocity, the normal injection velocity is 1000 m / s or less.

The gas flow G emitted from the gas outlet 4 is
High-speed fluid flows along the inclined surface parallel to the inclined surface. On the other hand, the slurry ejected from the slurry ejection port 5 so as to intersect with the flow direction of the gas flow G is pressed against the inclined surface by the gas flow flowing at high speed to become the thin film flow S. The thin film flow S flowing along the inclined surface normally flows at supersonic speed and leaves the inclined surface at the nozzle edge 6, and at the same time, becomes a droplet and is sprayed in a predetermined direction. At this time, it is preferable to collide with the other similarly formed thin film stream and atomize it as droplets in order to form smaller droplets. In FIG. 1, since the nozzle edge is provided in a ring shape around the nozzle, droplets are similarly sprayed in a ring shape. By spraying in an annular shape, the spray amount can be increased, that is, the production amount can be increased. It is preferable that the spraying direction is substantially horizontal because the nozzle can be easily designed. In addition, the substantially horizontal direction allows a width of approximately ± 40 ° with respect to the horizontal direction.

In the above method, since a large amount of droplets can be sprayed with one nozzle, productivity can be improved. Also, since the formed droplets are extremely fine,
The particle size of the lithium-transition metal composite oxide obtained by drying and calcining this can be reduced. The liquid droplet miniaturization technique itself is described in Japanese Patent No. 2797080, and the liquid droplet formation itself can be more easily carried out by referring to the above-mentioned known documents.

The slurry that has become droplets is dried. At the time of drying, it is preferable to introduce a drying gas from the upper part of the drying tower toward the lower part by downflow. With such a structure, the throughput per unit volume of the drying tower can be significantly improved. In addition, when spraying liquid droplets in a substantially horizontal direction, it is possible to greatly reduce the diameter of the drying tower by suppressing the liquid droplets that have been sprayed in the horizontal direction with downflow gas. Is possible. The drying gas temperature is usually 50 or higher, preferably 70 ° C. or higher, while it is usually 300.
C. or lower, preferably 250.degree. C. or lower. If the temperature is too high, due to the rapid drying of the droplets, it may not be possible to granulate well, or the resulting granulated particles will have many hollow structures, and the packing density of the powder will tend to decrease. If it is too low, problems such as powder sticking and blockage due to water condensation at the powder outlet may occur.

The granulated particles can be obtained by spray-drying in this manner, and the granulated particle diameter is preferably 50 μm or less in average particle diameter, more preferably 30 μm.
m or less. However, since it tends to be difficult to obtain a too small particle diameter, it is usually 4 μm or more, preferably 5 μm or more. The particle size of the granulated particles can be controlled by appropriately selecting the spray type, pressurized gas flow supply rate, slurry supply rate, drying temperature and the like.

The granulated particles obtained by such treatment are then mixed with a lithium source. By mixing a lithium source with the spray-dried granulated particles, the lithium source is selectively deposited on the surface during spray drying, and a shell of a lithium compound is generated on the particle surface, so that after drying, It is possible to effectively suppress the hollowing of the particles. As the lithium source to be mixed, Li ₂ CO ₃ , LiNO ₃ , LiO
H, LiOH / H ₂ O, LiI, CH ₃ COOLi, Li
₂ O, Li dicarboxylic acid, Li citric acid, Li fatty acid,
Alkyl lithium, lithium halide, etc. can be used. Of course, a plurality of types can be used together. Further, from the viewpoint of enhancing the uniformity of mixing and the reactivity during firing,
The particle size of the lithium source is usually 200 in terms of average particle size.
μm or less, preferably 100 μm or less, more preferably 30 μm or less. If a lithium source having an average particle size larger than this is used, the mixture becomes non-uniform and the reaction during firing becomes non-uniform, and it tends to be difficult to obtain a lithium-transition metal composite oxide powder with good performance. It is in. on the other hand,
The average particle size of the lithium source is usually 0.01 μm or more, preferably 0.1 μm or more. It may be preferable to reduce the average particle size of the lithium source too much from the viewpoint of uniformity of mixing and reactivity during firing, but it is industrially costly because of miniaturization. The method for mixing is not particularly limited, but a V-type rotary mixer, a conical rotary mixer, a vertical axis rotary mixer, a shovel blade rotary type mixer and the like can be used. The optimum mixing conditions (time, number of revolutions, etc.) differ greatly depending on the type of mixer used, so it cannot be specified unconditionally, but regarding the powder obtained after mixing, the content ratio of lithium and transition metal components is 1 g size. The standard deviation is 80% when 5 points are analyzed.
It is preferable to mix uniformly until the level reaches within 50%, preferably within 50%. When the standard deviation is larger than this, the reaction between lithium and the transition metal compound locally progresses, and it tends to be difficult to obtain a homogeneous lithium-transition metal composite oxide powder having good characteristics. The mixed powder thus obtained is then calcined. Although the firing temperature varies depending on the types of transition metals and substitution elements used as raw materials, it is usually 50
It is usually 0 ° C. or higher and 1000 ° C. or lower. If the temperature is too low, a long firing time tends to be required to obtain a lithium-transition metal composite oxide having good crystallinity. Further, if the temperature is too high, a crystal phase other than the intended lithium transition metal composite oxide is generated, or a lithium transition metal composite oxide with many defects is generated, which results in a capacity of a secondary battery. Or deterioration due to the collapse of the crystal structure due to charge / discharge may occur.

On the other hand, the firing time varies depending on the temperature, but is usually 30 minutes or more and 50 hours or less in the above temperature range. If the firing time is too short, it becomes difficult to obtain a lithium-transition metal composite oxide having good crystallinity, and if it is too long, it is not practical. In order to obtain a lithium-transition metal composite oxide with few crystal defects, it is preferable to cool slowly after the firing reaction, for example, 5 ° C./min. It is preferable to gradually cool at the following cooling rate.

The atmosphere during firing may 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.
For example, when producing a lithium-manganese composite oxide having a layered structure, it is preferable to carry out in a vacuum or in an inert atmosphere such as nitrogen or argon, LiCoO ₂ system, LiNiO ₂ system,
Alternatively, when producing a spinel type lithium manganese composite oxide or the like, it is preferable to carry out at least the slow cooling process in the air or an oxygen-containing atmosphere such as oxygen.

The heating device used for firing is the above-mentioned temperature,
There is no particular limitation as long as the atmosphere can be achieved, and for example, a box furnace, a tubular furnace, a tunnel furnace, a rotary kiln or the like can be used. The lithium-transition metal composite oxide thus obtained preferably has a primary particle size of 0.1 to 3 μm, and a secondary particle size of 1 to 50 μm, particularly 4 to 50 μm. Further, the specific surface area due to nitrogen adsorption is preferably 0.1 to ⁵ m ² / g. The size of the primary particles can be controlled by the firing temperature, the firing time and the like, and the particle diameter of the primary particles can be increased by increasing one or more of these. The particle size of the secondary particles can be controlled by the spraying conditions such as the gas-liquid ratio in the pulverization or spray drying step before firing. The specific surface area depends on the particle size of the primary particles and 2
It can be controlled by the particle size of the secondary particles, and can be reduced by increasing the particle size of the primary particles and / or the particle size of the secondary particles. Also, the packing density is preferably 1.50 g / cc or more in terms of tap density (after 200 taps).

Examples of the lithium transition metal composite oxide to be produced include various ones such as lithium nickel composite oxide, lithium cobalt composite oxide and lithium manganese composite oxide, which can be represented by the following general formula. I can.

[0026]

Embedded image _{Li x M y O 2 ± δ} ( here, x is the number of 0.4 to 1.2, y is 0.8 to 1.
Number of 1, M is Mn, Ni, Co, Al, Ti, V, C
at least one element selected from the group consisting of r, Fe, Cu, Zn, Mg, Ga, and Zr, and δ is -0.1 to 0.
The metal element M is at least Mn, N
It is preferable to contain at least one transition metal element selected from the group consisting of i and Co. By using the obtained lithium-transition metal composite oxide as an active material, electrodes and batteries can be manufactured. For example, as an example of a battery, a lithium secondary battery having a positive electrode, a negative electrode, and an electrolyte can be given. Specifically, there can be mentioned a secondary battery in which an electrolyte is present between the positive electrode and the negative electrode, and a separator is disposed between them so that the positive electrode and the negative electrode do not come into contact with each other as necessary.

The positive electrode is a mixture of the lithium-transition metal composite oxide (positive electrode active material) obtained in the present invention, a binder and, if necessary, a conductive agent, and a certain amount of a solvent for uniformly dispersing them. It can be obtained by coating the mixture on a current collector and drying it after being mixed with to form a paint. Examples of the conductive material used here include natural graphite, artificial graphite, and acetylene black, and as the binder, polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl acetate, polymethylmethacrylate, polyethylene, nitrocellulose, etc. However, examples of the solvent for dispersion include N-methylpyrrolidone, tetrahydrofuran, dimethylformamide and the like. Examples of the material of the current collector include aluminum and stainless steel. The positive electrode is
Usually, after forming the positive electrode mixture layer on the current collector, it is usually compacted by a roller press or other method.

On the other hand, as the negative electrode, a carbon material (natural graphite, pyrolytic carbon, etc.) coated on a collector such as Cu, a lithium metal foil, a lithium-aluminum alloy, or the like can be used. The electrolyte used in the lithium secondary battery is a non-aqueous electrolytic solution, and is usually prepared by dissolving an electrolytic salt in a non-aqueous solvent. Electrolytic salts include LiClO ₄ , LiAsF ₆ ,
Examples thereof include lithium salts such as LiPF ₆ , LiBF ₄ , LiBr, and LiCF ₃ SO ₃ . Further, as the non-aqueous solvent,
Tetrahydrofuran, 1,4-dioxane, dimethylformamide, acetonitrile, benzonitrile, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate and the like can be mentioned. These electrolytic salts and non-aqueous solvents may be used alone or in combination of two or more.

As the separator used in the battery,
Examples thereof include polymers such as polytetrafluoroethylene, polyethylene, polypropylene, polyester, and non-woven fabric filters such as glass fibers, and composite non-woven fabric filters of glass fibers and polymer fibers.

[0030]

EXAMPLES The method of the present invention will be described more specifically below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. <Example 1> NiO, Co (OH) ₂ , and AlOOH
Ni: Co: Al = 0.80: 0.15: 0.05 (molar ratio) was weighed, and pure water was added to this to prepare a slurry having a solid content concentration of 30% by weight. While stirring this slurry, using a circulation type medium stirring type wet pulverizer,
After pulverizing until the average particle size of the solid content in the slurry becomes 0.3 μm, a spray dryer (manufactured by Fujisaki Electric Co., Ltd.) provided with a nozzle having a droplet refining mechanism as shown in FIGS. 1 and 2. Micro Mist Dryer MDP-0
No. 50, a circle type nozzle as a nozzle type, and a drying tower size of 2500 mmφ × 4800 mmH) were used for spray drying.

At this time, the dry gas was supplied by down-flow, the dry gas introduction amount was 23 m ³ / min, and the dry gas inlet temperature was 90 ° C. Also, as a spray nozzle, the diameter
Use a type that is capable of horizontal spraying in the direction of 360 ° (annular) with a diameter of 30 mm, and has a nozzle slurry outlet clearance of 60
The clearance at the pressurized gas outlet for atomizing the slurry was set to 0 μm and 350 μm. The slurry supply rate is 700 g / min, and the pressurized gas flow supply rate is 13
00 L / min (the gas linear velocity of the gas flow is 330 m /
s). The exhaust gas temperature when spray-dried under these conditions is 45
It was ℃. The dried granulated particles collected by the cyclone were then mixed with LiOH having an average particle size of 1 μm. As a mixing ratio, in the finally obtained lithium composite oxide composition, Li: Ni: Co: Al = 1.05:
0.80: 0.15: 0.05 (molar ratio), and a total of 6 kg of powder was charged into a shovel blade rotary mixer (Matsubo's Lodige Mixer M-20 model), and the shovel rotation speed was adjusted. 230 rpm, chopper speed 30
It was carried out at 00 rpm for 20 minutes while introducing nitrogen gas into the mixer. The obtained mixed powder was fired in an oxygen atmosphere at 750 ° C. for 12 hours. As a result, substantially spherical granulated particles having an average particle diameter of 7.2 μm and a maximum particle diameter of 21 μm were obtained. When X-ray diffraction was measured, it was confirmed to have a structure of a layered lithium nickel-based composite oxide. The particle size distribution was measured using a laser diffraction / scattering particle size distribution measurement device (LA910 manufactured by HORIBA). 10 g of this powder was placed in a 25 ml glass graduated cylinder, and after tapping 200 times, the powder packing density (tap density) was measured and found to be 2.0 g / cc. Furthermore, 3 g of the powder was filled in a cylindrical cylinder made of SUS, the inner surface of 25 mmφ of which was coated with polytetrafluoroethylene, and the powder packing density after pressing with a load of 400 kgf / cm ² was measured to be 3.1 g /
It was cc. The positive electrode active material 10 thus obtained
g, acetylene black (AB), and polyvinylidene fluoride (PVDF) were dispensed into a 50 cc polyethylene container using N-methyl-2-pyrrolidone as a solvent to a solid concentration of 40 wt%. The compounding ratio of each component at this time was positive electrode active material: AB: PVDF = 90: 5: 5 (wt%). Further, 20 g of 1 mmφ zirconia beads was added, the container was tightly closed, and the container was set on a shaker and mixed for 30 minutes. The mixed coating solution of the positive electrode agent was applied onto an aluminum electrode sheet having a thickness of 21 μm using an applicator having a clearance of 350 μm, dried at 120 ° C., and punched with a punch to obtain 12 mmφ positive electrode pellets. The punched pellets are 24 MPa in a hand press machine.
The consolidation treatment was performed for 1 minute at the pressure of.

A coin-type battery was assembled using the pellets and the battery was evaluated. At this time, lithium metal was used as the negative electrode material, and a solution prepared by dissolving 1 mol / L lithium hexafluorophosphate (LiPF ₆ ) in a 3: 7 mixed solvent of ethylene carbonate and diethyl carbonate was used as the electrolytic solution. . Using this battery, the charge / discharge capacity was measured when the battery was charged / discharged in the range of 3.0-4.2 V at a current density of 0.2 mA / cm ² , and the charge capacity was 202 mAh /
It was confirmed that it had good characteristics such as g, discharge capacity of 175 mAh / g, and charge / discharge efficiency of 87%.

Regarding the liquid droplet refining technology, since the velocity of the pressurized gas flow and the slurry thin film flow is in the supersonic region, particularly with respect to the atomization of the spray in a slurry system containing solids having different specific gravities. Regarding the obtained granulated particles, it was feared that the battery performance might be deteriorated due to uneven distribution of some compounds, compositional variation, etc., but it was found that very good battery characteristics were obtained by the above examples.

[0034]

According to the present invention, a lithium-transition metal composite oxide having a high packing density and good battery performance can be mass-produced at low cost. Further, by using the lithium transition metal composite oxide having an increased packing density as the positive electrode active material of the lithium ion secondary battery, the energy density per unit volume is improved,
In the case of batteries of the same size, a battery with a high capacity can be obtained, and with the same energy capacity, a battery with a smaller size can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic side view showing a nozzle portion of a spray dryer that can be used for spray drying, with a partial cross section exposed.

FIG. 2 is a schematic cross-sectional view showing an enlarged nozzle tip of FIG. 1 together with a gas flow and a slurry flow.

[Explanation of symbols]

1 nozzle 2 slope 4 Gas outlet 5 Slurry outlet 7 gas supply pipe 8 Slurry supply pipe

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Claims (13)

[Claims] 1. A method for producing a lithium-transition metal composite oxide, which comprises spray-drying a slurry containing a transition metal source, mixing the slurry with a lithium source, and subjecting the mixture to a calcination treatment. 1) By supplying the slurry so as to intersect a gas flow flowing along a smooth surface, a thin film flow of the slurry is formed between the smooth surface and the gas flow, and (2) the thin film flow is A method for producing a lithium-transition metal composite oxide, characterized in that droplets are formed by separating from the smooth surface and (3) the droplets are dried. 2. Spray drying is performed at a drying gas temperature of 50 to 300.
The production method according to claim 1, which is carried out under the condition of ° C. 3. The injection velocity of the gas flow is 100 to 100% of the linear gas velocity.
It is 1000 m / s, The manufacturing method of Claim 1 or 2. 4. The average particle size of the solid matter in the slurry is 2 μm.
The manufacturing method according to any one of claims 1 to 3, which is m or less. 5. The production method according to claim 1, wherein the average particle size of the obtained lithium-transition metal composite oxide is 4 to 50 μm. 6. The method according to claim 1, wherein the droplets are sprayed in a ring shape.
The manufacturing method according to any one of 1. 7. The manufacturing method according to claim 1, wherein the droplets are sprayed in a substantially horizontal direction, and the sprayed droplets are introduced with a dry gas by downflow. 8. A slurry containing a transition metal source containing at least one transition metal element selected from the group consisting of Mn, Ni and Co, and Al, Ti, V, Cr, Fe, Cu, Z.
The method according to claim 1, further comprising a metal element source containing at least one metal element selected from the group consisting of n, Mg, Ga, and Zr. 9. The metal element source is Al, Ti, V, Cr,
Oxides, hydroxides, oxyhydroxides, nitrates, sulfates, carbonates, dicarboxylates, fatty acid salts and ammonium salts of elements selected from the group consisting of Fe, Cu, Zn, Mg, Ga, and Zr. The method according to claim 8, which is at least one selected from the group consisting of: 10. The lithium source is Li ₂ CO ₃ , LiNO.
₃ , LiOH, LiOH.H ₂ O, LiI, CH ₃ COO
The manufacturing method according to claim 1, wherein the manufacturing method is at least one selected from the group consisting of Li, Li ₂ O, Li dicarboxylic acid, Li citric acid, Li fatty acid, alkyl lithium, and lithium halide. 11. The lithium-transition metal composite oxide according to claim 1, which is represented by the following general formula (I).
Manufacturing method described in. ## STR1 ## _{Li x M y O 2 ± δ} (I) ( here, x is the number of 0.4 to 1.2, y is 0.8 to 1.
Number of 1, M is Mn, Ni, Co, Al, Ti, V, C
at least one element selected from the group consisting of r, Fe, Cu, Zn, Mg, Ga, and Zr, and δ is -0.1 to 0.
Represents the number of 1) 12. A coating material containing a mixture containing a lithium-transition metal composite oxide obtained by the method according to claim 1 and a binder, and a solvent, is applied onto a current collector. -A method of manufacturing an electrode, which comprises drying. 13. A lithium secondary battery using the lithium transition metal composite oxide obtained by the method according to claim 1 as a positive electrode active material.