JP2007238435A - Manufacturing process of lithium transition metal complex oxide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a process by which a lithium transition metal complex oxide having a high filling density is inexpensively mass-produced. <P>SOLUTION: The manufacturing process of the lithium transition metal complex oxide includes spray-drying a slurry containing a lithium source and a transition metal source and firing the dried material. In the spray dry process, (1) the slurry is fed in a way to cross the flow of a gas flowing along a smooth surface to form a thin filmy flow of the slurry between the smooth surface and the gas flow, (2) the thin filmy flow is separated from the smooth surface to form liquid drops and (3) the liquid drops are dried. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  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.

Examples of positive electrode active materials for lithium ion secondary batteries include lithium transition metal composite oxides such as LiCoO ₂ and LiNiO ₂ which are layered composite oxides and LiMn ₂ O ₄ based compounds having a spinel structure. Can be obtained, and has a high energy density, so that it has already been put into wide use or has been put into 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 positive electrode active material packing density, the higher the energy density per unit volume. Can produce a high-capacity battery, and if the battery has the same energy capacity, there are advantages such as miniaturization.

Accordingly, a method has been proposed in which positive electrode active material particles are granulated into a spherical shape to improve the filling property. For example, a method of spray drying a slurry as a raw material, a method of spray pyrolysis of 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. The active material particles used in such applications are used from the viewpoint of the uniformity of the coating film. It will be necessary to make the particles smaller.

  However, it is difficult to form small-diameter particles by spraying. In particular, when the average particle size is 10 μm or less, there is a problem in the conventional method for droplet miniaturization (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, since the productivity per nozzle is low, the size of the apparatus is increased due to an increase in the number of nozzles. However, it was not always sufficient in terms of low-cost production.

Further, according to the study by the present inventors, it has been found that there are the following problems when spray drying is performed in the production of the lithium transition metal composite oxide.
That is, if a lithium source is present in the slurry during spray drying, the water-soluble lithium compound is selectively deposited on the surface, and a shell of lithium compound is generated on the particle surface. As a result, 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 of a lithium ion secondary battery, particularly a method for mass-producing a lithium transition metal composite oxide having a high packing density at low cost. It is the purpose.
As a result of intensive studies on a cheaper manufacturing method for increasing the bulk density of the lithium transition metal composite oxide, the present inventors have (1) a smooth surface as a method for forming slurry droplets for spray drying. A method of separating the thin film flow from the smooth surface after forming a thin film flow of slurry between the smooth surface and the gas flow by supplying the slurry so as to intersect the gas flow flowing along And (2) as a method for mixing raw materials, the present invention was completed by finding that it is effective to combine the granulated particles obtained by spray drying and a method of mixing lithium.

That is, the gist of the present invention resides in the following (1) to (14).
(1) In the method for producing a lithium transition metal composite oxide, the slurry containing the transition metal source is spray-dried, mixed with a lithium source, and the mixture is subjected to a firing treatment.
By supplying the slurry so as to intersect a gas flow flowing along a smooth surface, a thin film flow of slurry is formed between the smooth surface and the gas flow,
Forming droplets by separating the thin film stream from the smooth surface;
A method for producing a lithium transition metal composite oxide, comprising drying the droplets. (2) The production method according to (1), wherein the spray drying is performed under a condition of a drying gas temperature of 50 to 300 ° C.
(3) The production method according to (1) or (2), wherein the gas flow injection speed is from 100 to 1000 m / s.
(4) The manufacturing method in any one of (1)-(3) whose average particle diameter of the solid substance in a slurry is 2 micrometers or less.
(5) The production method according to any one of (1) to (4), wherein the average particle size of the obtained lithium transition metal composite oxide is 4 to 50 μm.
(6) The manufacturing method according to any one of (1) to (5), in which droplets are sprayed in an annular shape.
(7) The manufacturing method according to any one of (1) to (6), wherein the droplets are sprayed in a substantially horizontal direction, and the sprayed droplets are introduced with a dry gas in a down flow.
(8) 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, Mg, Ga, and The manufacturing method in any one of (1)-(7) containing the metal element source containing the at least 1 sort (s) of metal element chosen from the group which consists of Zr.
(9) An oxide, hydroxide, oxyhydroxide, nitrate of an element selected from the group consisting of Al, Ti, V, Cr, Fe, Cu, Zn, Mg, Ga, and Zr , Sulfate, carbonate, dicarboxylate, fatty acid salt and ammonium salt, (8).
(10) The lithium source is Li ₂ CO ₃ , LiNO ₃ , LiOH, LiOH.H ₂ O, LiI, CH ₃ COOLi, Li ₂ O, Licarboxylic acid Li, Li citrate, Fatty acid Li, Alkyl lithium, Lithium halide The manufacturing method in any one of (1)-(9) which is at least 1 type chosen from the group which consists of.
(11) The production method according to any one of (1) to (10), wherein the lithium transition metal composite oxide is represented by the following general formula (I).

（ただし、ｘは０．４〜１．２の数、ｙは０．８〜１．１の数、ＭはＭｎ、Ｎｉ、Ｃｏ、Ａｌ、Ｔｉ、Ｖ、Ｃｒ、Ｆｅ、Ｃｕ、Ｚｎ、Ｍｇ、Ｇａ、Ｚｒからなる群から選ばれる少なくとも１種の元素、δは−０．１〜０．１の数を表す）（１２）（１）〜（１１）のいずれか１つに記載の方法で得られたリチウム遷移金属複合酸化物とバインダーとを有する合剤と溶媒とを含む塗料を、集電体上に塗布・乾燥することを特徴とする電極の製造方法。
（１３）（１）〜（１１）のいずれか１つに記載の方法で得られたリチウム遷移金属複合酸化物を正極活物質として使用したリチウム二次電池。

(Where x is a number from 0.4 to 1.2, y is a number from 0.8 to 1.1, M is Mn, Ni, Co, Al, Ti, V, Cr, Fe, Cu, Zn, Mg , Ga, Zr, at least one element selected from the group consisting of δ represents a number of −0.1 to 0.1) (12) The method according to any one of (1) to (11) A method for producing an electrode, comprising: applying and drying a paint containing a mixture containing a lithium-transition metal composite oxide and a binder obtained in 1 above and a solvent on a current collector.
(13) A lithium secondary battery using the lithium transition metal composite oxide obtained by the method according to any one of (1) to (11) as a positive electrode active material.

According to the present invention, a lithium transition metal composite oxide having a high filling density and good battery performance can be produced in a large amount at a low cost. In addition, by using the lithium transition metal composite oxide having such a high packing density as the positive electrode active material of the lithium ion secondary battery, the energy density per unit volume is improved and the batteries of the same size are used. In this case, a high-capacity battery can be obtained, and if the energy capacity is the same, a smaller battery can be obtained.

  The slurry subjected to spray drying has at least one 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 the undissolved solids in the slurry is usually 2 μm or less, preferably 1 μm or less, more preferably 0.5 μm or less. If the average particle size of the solids in the slurry is too large, the sphericity tends to decrease and the final powder packing density tends to be low. This tendency is particularly remarkable when trying to produce granulated particles having an average particle diameter of 50 μm or less. As a method for controlling the average particle size of the solid matter in the slurry, the raw material powder is previously dry-ground by a ball mill, a jet mill, etc., and this is dispersed in a dispersion medium. A wet pulverization method using a mold pulverizer or the like can be used. In addition, since it is not preferable to make particles smaller than necessary because it leads to an increase in the cost of pulverization, 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. To do.

When a lithium source is present in the slurry, the productivity is relatively lowered and the packing density of the obtained lithium transition metal composite oxide tends to be lowered. However, a part of the lithium source used as a raw material is reduced. It 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 Li, citrate Li, fatty acid Li, alkyllithium, lithium halogen A compound or the like can be used. Of course, multiple species can be used in combination. However, since the above-mentioned tendency becomes obvious when a large amount of lithium source is contained in the slurry, it is usually 50% by weight or less, preferably 30% by weight or less, more preferably 10% by weight or less of the lithium source to be used. In the slurry. Most preferably, the lithium source is not contained in the slurry and is used in its entirety when mixed 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. Preferably it contains manganese, nickel or cobalt. Usually, transition metal oxides include organic acid salts such as transition metal oxides, carbonates, nitrates, sulfates, acetic acid, hydroxides, oxyhydroxides, halides, and the like. Of course, these can be used in combination.

  The slurry may further contain a compound containing an element other than the transition metal source such as Al, Zn, Mg, and Ga. Further, when at least one selected from the group consisting of nickel, cobalt and manganese is used as the 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. Therefore, a metal element source containing elements such as Al, Ti, V, Cr, Fe, Cu, Zn, Mg, Ga, and Zr can be contained in the slurry. Specifically, the metal element source includes at least one selected from oxides, hydroxides, oxyhydroxides, nitrates, sulfates, carbonates, dicarboxylates, fatty acid salts and ammonium salts of the above elements. Can do.

  The resulting slurry is subjected to spray drying. In the present invention, the spray drying is performed by (1) supplying the slurry so as to intersect with the gas flow flowing along the smooth surface, so that a thin film flow of slurry is formed between the smooth surface and the gas flow. (2) forming a droplet by separating the thin film stream from the smooth surface; and (3) drying the droplet.

  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 (the hatched portion shows a partially cut section), and FIG. 2 shows the nozzle of FIG. It is typical sectional drawing which expands a front-end | tip and shows with a gas flow and the flow of a slurry. The cylindrical nozzle 1 is provided with a nozzle tip 3 having a smooth inclined surface 2 in an annular shape around the cylinder. The nozzle tip 3 is provided with a gas outlet 4 for supplying a high-speed gas flow flowing along the inclined surface 2 through the gas supply pipe 7 toward the inclined surface 2. The nozzle tip 3 is provided with a slurry outlet 5 for supplying the slurry through a slurry supply pipe 8 so that the emitted slurry intersects the flow direction of the gas flow emitted along the inclined surface. ing.

  Air, nitrogen, or the like can be used as the gas supplied as the gas flow, but air is usually used. These are preferably used under pressure. The gas flow is injected at a gas linear velocity of usually 100 m / s or more, preferably 200 m / s or more, more preferably 300 m / s or more. If it is too small, it is difficult to form appropriate droplets. However, since it is difficult to obtain a linear velocity that is too high, the normal injection speed is 1000 m / s or less.

  The gas flow G emitted from the gas outlet 4 flows at high speed along the inclined surface in parallel with the inclined surface. On the other hand, the slurry emitted from the slurry outlet 5 so as to intersect the flow direction of the gas flow G is pressed against the inclined surface by the gas flow flowing at high speed to be a thin film flow S. The thin film flow S flowing along the inclined surface normally flows at supersonic speed, and at the same time leaves the inclined surface at the nozzle edge 6 and becomes droplets and sprayed in a predetermined direction. At this time, it is preferable to collide with another thin film flow formed in the same manner and spray as droplets in order to form smaller droplets. In FIG. 1, since the nozzle edge is provided in an annular shape around the nozzle, droplets are similarly sprayed in an annular shape. By spraying in an annular shape, the spray amount can be increased, that is, the production amount can be increased. The direction of spraying is preferably substantially horizontal because nozzle design is easy. The substantially horizontal direction allows a width of about ± 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. Further, since the formed droplets are extremely fine, the particle size of the lithium transition metal composite oxide obtained by drying and firing the droplets can be reduced.
Note that the droplet refinement technique itself is described in Japanese Patent No. 2797080, and the formation of the droplet itself can be more easily performed by referring to the above-mentioned known documents.

  The slurry in the form of droplets is dried. At the time of drying, it is preferable to introduce the drying gas by downflow from the upper part of the drying tower to the lower part. By setting it as such a structure, the processing amount per unit capacity of a drying tower can be improved significantly. In addition, when spraying droplets in a substantially horizontal direction, it is possible to greatly reduce the diameter of the drying tower by suppressing the droplets sprayed in the horizontal direction with a downflow gas, and to manufacture inexpensively and in large quantities. Is possible. The drying gas temperature is usually 50 or higher, preferably 70 ° C. or higher, and usually 300 ° C. or lower, preferably 250 ° C. or lower. If the temperature is too high, granulation cannot be performed well due to rapid drying of the droplets, and the resulting granulated particles have a lot of hollow structures, which tends to reduce the packing density of the powder, If it is too low, problems such as powder sticking and blockage due to moisture condensation at the powder outlet may occur.

  The granulated particles are obtained by spray drying in this manner, and the granulated particle diameter is preferably 50 μm or less, more preferably 30 μm or less in terms of average particle diameter. However, since it tends to be difficult to obtain a too small particle size, it is usually 4 μm or more, preferably 5 μm or more. The particle diameter of the granulated particles can be controlled by appropriately selecting the spray format, 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 the lithium source with the granulated particles after spray drying, the lithium source selectively deposits on the surface during spray drying, resulting in the formation of lithium compound shells on the particle surface. It is possible to effectively suppress the hollowing of the particles. Lithium sources to be mixed include Li ₂ CO ₃ , LiNO ₃ , LiOH, LiOH · H ₂ O, LiI, CH ₃ COOLi, Li ₂ O, Licarboxylic acid Li, Li citrate, Fatty acid Li, Alkyl lithium, Lithium halide Etc. can be used. Of course, multiple species can be used in combination. From the viewpoint of improving the uniformity of mixing and the reactivity during firing, the particle size of the lithium source is usually 200 μm or less, preferably 100 μm or less, more preferably 30 μm or less in terms of the average particle size. If a lithium source having a larger average particle size than this is used, the mixing becomes uneven, the reaction during firing also becomes uneven, 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. To make the average particle size of the lithium source too small may be preferable from the viewpoint of uniformity of mixing and reactivity at the time of firing, but it is very expensive for industrial miniaturization. A method for mixing is not particularly limited, but examples thereof include a V-type rotary mixer, a conical rotary mixer, a vertical shaft rotary mixer, and a shovel blade rotary mixer. The optimum mixing conditions (time, number of revolutions) etc. vary greatly depending on the type of mixer used, so it cannot be specified unconditionally, but the content ratio of lithium and transition metal component is 1g size for the powder obtained after mixing. When the 5-point analysis is performed, it is preferable to mix uniformly until reaching a level where the standard deviation is within 80%, preferably within 50%. When the standard deviation is larger than this, the reaction between lithium and the transition metal compound proceeds locally, and it tends to be difficult to obtain a lithium transition metal composite oxide powder having uniform and good characteristics.

  The mixed powder thus obtained is then fired. The firing temperature is usually 500 ° C. or higher and usually 1000 ° C. or lower, although it varies depending on the type of transition metal and substitution element used as a raw material. If the temperature is too low, a long baking time tends to be required in order to obtain a lithium transition metal composite oxide having good crystallinity. In addition, if the temperature is too high, a crystal phase other than the target lithium transition metal composite oxide is generated, or a lithium transition metal composite oxide with many defects is generated. Or degradation due to the collapse of the crystal structure due to charge / discharge.

On the other hand, 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 lithium transition metal composite oxide having good crystallinity, and it is not practical to be too long.
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 slowly cool at the following cooling rate.

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. For example, when producing a lithium manganese composite oxide having a layered structure, it is preferably performed in a vacuum or in an inert atmosphere such as nitrogen or argon, and LiCoO ₂ type, LiNiO ₂ type, or spinel type lithium manganese composite oxide Is preferably carried out in an oxygen-containing atmosphere such as air or oxygen at least during the slow cooling process.

The heating device used for firing is not particularly limited as long as the above temperature and atmosphere can be achieved. 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 the secondary particle size is preferably 1 to 50 μm, particularly preferably 4 to 50 μm. Furthermore, it is preferable that the specific surface area by nitrogen adsorption is 0.1-5 m < ² > / g. The size of the primary particles can be controlled by the firing temperature, the firing time, and the like. By increasing one or more of these, the particle size of the primary particles can be increased. The particle diameter of the secondary particles can be controlled by spraying conditions such as gas-liquid ratio in the pulverization before spraying or spray drying process. The specific surface area can be controlled by the primary particle size and the secondary particle size, and decreases by increasing the primary particle size and / or the secondary particle size. The filling density is preferably 1.50 g / cc or more in terms of tap density (after 200 taps).

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

（ただし、ｘは０．４〜１．２の数、ｙは０．８〜１．１の数、ＭはＭｎ、Ｎｉ、Ｃｏ、Ａｌ、Ｔｉ、Ｖ、Ｃｒ、Ｆｅ、Ｃｕ、Ｚｎ、Ｍｇ、Ｇａ、Ｚｒからなる群から選ばれる少なくとも１種の元素、δは−０．１〜０．１の数を表す）
上記金属元素Ｍは、少なくともＭｎ、Ｎｉ及びＣｏからなる群から選ばれる少なくとも一種の遷移金属元素を含有するのが好ましい。

(Where x is a number from 0.4 to 1.2, y is a number from 0.8 to 1.1, M is Mn, Ni, Co, Al, Ti, V, Cr, Fe, Cu, Zn, Mg At least one element selected from the group consisting of Ga, Zr, and δ represents a number of -0.1 to 0.1)
The metal element M preferably contains at least one transition metal element selected from the group consisting of Mn, Ni and Co.

  Using the obtained lithium transition metal composite oxide as an active material, an electrode and a battery can be produced. For example, a lithium secondary battery having a positive electrode, a negative electrode, and an electrolyte can be given as an example of the battery. Specifically, there can be mentioned a secondary battery in which an electrolyte exists between the positive electrode and the negative electrode, and a separator is disposed between the positive electrode and the negative electrode 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 mixed with a certain amount of a solvent for uniformly dispersing them. It can be obtained by coating and drying on a current collector after forming a paint. Examples of the conductive material used here include natural graphite, artificial graphite, and acetylene black. Examples of the binder include polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl acetate, polymethyl methacrylate, polyethylene, and nitrocellulose. 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 consolidated by a roller press or other methods after forming the positive electrode mixture layer on the current collector.

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

Examples of the separator used in the battery include a polymer such as polytetrafluoroethylene, polyethylene, polypropylene, and polyester, or a nonwoven fabric filter such as glass fiber, or a composite nonwoven fabric filter composed of glass fiber and polymer fiber.

Hereinafter, the method of the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded.
<Example 1>
NiO, Co (OH) ₂ , and AlOOH are mixed with Ni: Co: Al = 0.80: 0.15: 0.
. It weighed so that it might become 05 (molar ratio), and the pure water was added to this, and the slurry with a solid content concentration of 30 weight% was prepared. While stirring this slurry, using a circulating medium agitation type wet pulverizer, the slurry was pulverized until the average particle size of the solid content in the slurry became 0.3 μm, and then the liquid as shown in FIGS. Spray drying was performed using a spray dryer (manufactured by Fujisaki Electric Co., Ltd., Micro Mist Dryer MDP-050, nozzle type is a circle edge nozzle, drying tower size is 2500 mmφ × 4800 mmH) provided with a nozzle having a droplet refining mechanism. .

The drying gas at this time was supplied by downflow, the amount of drying gas introduced was 23 m ³ / min, and the drying gas inlet temperature was 90 ° C. In addition, as the spray nozzle, use a type with a diameter of 30 mmφ that can be sprayed horizontally in the 360 ° (annular) direction, the nozzle outlet clearance is 600 μm, and the pressurized gas outlet clearance for making the slurry finer Set to 350 μm. The slurry supply rate was 700 g / min, and the pressurized gas flow supply rate was 1300 L / min (the gas linear velocity of the gas flow was 330 m / s). The exhaust gas temperature when spray-dried under these conditions was 45 ° C. The dried granulated particles collected by the cyclone were then mixed with LiOH having an average particle diameter of 1 μm. As the mixing ratio, the lithium composite oxide composition finally obtained was Li: Ni: Co: Al = 1.05: 0.80: 0.15: 0.05 (molar ratio), and the total Then, 6 kg of powder was charged into an excavator blade rotating type mixer (Midgebo's Redige mixer M-20 type), and the excavator was rotated at 230 rpm and the chopper was rotated at 3000 rpm for 20 minutes while introducing nitrogen gas into the mixer. . The obtained mixed powder was fired at 750 ° C. for 12 hours in an oxygen atmosphere. 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 layered lithium nickel composite oxide structure. The particle size distribution was measured using a laser diffraction / scattering particle size distribution measuring apparatus (LA910 manufactured by HORIBA). 10 g of this powder was put into 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 powder was filled in a SUS cylindrical cylinder whose inner surface of 25 mmφ was coated with polytetrafluoroethylene, and the powder filling density after pressing with a load of 400 kgf / cm ² was measured to be 3.1 g / cc.

  A 50 cc polyethylene container having 10 g of the positive electrode active material thus obtained, acetylene black (AB), polyvinylidene fluoride (PVDF) and N-methyl-2-pyrrolidone as a solvent so as to have a solid concentration of 40 wt%. Sorted into 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 were added, the container was sealed, and the mixture was set on a shaker and mixed for 30 minutes. The mixed positive electrode coating solution 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 out with a punch to obtain a 12 mmφ positive electrode pellet. The punched pellets were subjected to a consolidation process for 1 minute at a pressure of 24 MPa using a hand press.

Using this pellet, a coin-type battery was assembled and battery evaluation was performed. At this time, lithium metal was used as the negative electrode material, and a solution of 1 mol / L lithium hexafluorophosphate (LiPF ₆ ) dissolved in a 3: 7 mixed solvent of ethylene carbonate and diethyl carbonate was used as the electrolyte. . Using this battery, when charging / discharging capacity at a current density of 0.2 mA / cm ² in a range of 3.0-4.2 V was measured, a charging capacity of 202 mAh / g, a discharging capacity of 175 mAh / g, It was confirmed that it has good characteristics with a charge / discharge efficiency of 87%.

  The droplet refinement technique can be obtained because the velocity of the pressurized gas flow and the slurry thin film flow is in the supersonic region, particularly regarding spray refinement in a slurry system containing solids having different specific gravity. Regarding the granulated particles, there was concern about the deterioration of battery performance due to the uneven distribution of some compounds, composition fluctuations, etc., but it was found that the above examples can provide very good battery characteristics.

The typical side view which shows the nozzle part of the spray dryer which 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 Inclined Surface 4 Gas Outlet 5 Slurry Outlet 7 Gas Supply Pipe 8 Slurry Supply Pipe

Claims (13)

In the method for producing a lithium transition metal composite oxide, the slurry containing the transition metal source is spray-dried, mixed with the lithium source, and the mixture is subjected to a firing treatment.
In the spray drying, (1) by supplying the slurry so as to intersect the gas flow flowing along the smooth surface, a thin film flow of slurry is formed between the smooth surface and the gas flow. 2) A method for producing a lithium transition metal composite oxide, comprising: forming a droplet by separating the thin film flow from the smooth surface; and (3) drying the droplet.   The production method according to claim 1, wherein the spray drying is performed under conditions of a drying gas temperature of 50 to 300 ° C.   The production method according to claim 1 or 2, wherein an injection speed of the gas flow is a gas linear velocity of 100 to 1000 m / s.   The production method according to any one of claims 1 to 3, wherein an average particle size of the solid matter in the slurry is 2 µm or less.   The manufacturing method according to any one of claims 1 to 4, wherein an average particle size of the obtained lithium transition metal composite oxide is 4 to 50 µm.   The manufacturing method according to claim 1, wherein the droplets are sprayed in an annular shape.   The manufacturing method according to any one of claims 1 to 6, wherein the droplets are sprayed in a substantially horizontal direction, and the sprayed droplets are introduced into the drying gas by downflow.   The slurry is a transition metal source containing at least one transition metal element selected from the group consisting of Mn, Ni and Co, and a group consisting of Al, Ti, V, Cr, Fe, Cu, Zn, Mg, Ga, and Zr. The manufacturing method in any one of the Claims 1 thru | or 7 containing the metal element source containing the at least 1 sort (s) of metal element chosen.   The metal element source is an oxide, hydroxide, oxyhydroxide, nitrate, sulfate of an element selected from the group consisting of Al, Ti, V, Cr, Fe, Cu, Zn, Mg, Ga, and Zr The production method according to claim 8, which is at least one selected from the group consisting of carbonate, dicarboxylate, fatty acid salt and ammonium salt. Lithium source is Li ₂ CO ₃ , LiNO ₃ , LiOH, LiOH.H ₂ O, LiI, CH ₃
The production method according to claim 1, which is at least one selected from the group consisting of COOLi, Li ₂ O, dicarboxylic acid Li, citrate Li, fatty acid Li, alkyllithium, and lithium halide. The method according to any one of claims 1 to 10, wherein the lithium transition metal composite oxide is represented by the following general formula (I).

(Where x is a number from 0.4 to 1.2, y is a number from 0.8 to 1.1, M is Mn, Ni, Co, Al, Ti, V, Cr, Fe, Cu, Zn, Mg At least one element selected from the group consisting of Ga, Zr, and δ represents a number of -0.1 to 0.1) Applying and drying on a current collector a paint containing a mixture having a lithium transition metal composite oxide and a binder obtained by the method according to any one of claims 1 to 11 and a solvent. A method for producing an electrode.   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.

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