JP2011233340A - Method for manufacturing electrode active material for storage element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an electrode active material for a storage element in a short time.SOLUTION: In the method for manufacturing an electrode active material for a storage element, a microwave furnace is used. The microwave furnace includes at least two inverter-controlled microwave oscillators which are arranged so that microwave irradiation regions are overlapped with each other in one region and are operated in a mutually decoupled state. A mixture of raw material components is supplied to the irradiation regions to be heated by the microwave furnace.

Description

  The present invention relates to a method for producing an electrode active material for a storage element.

  In recent years, lithium ion secondary batteries have high output and high energy density, and are attracting attention not only as portable devices but also as medium- and large-sized storage batteries for in-vehicle charging / discharging systems and power sources, power storage and supply systems, etc. ing. In such a lithium ion secondary battery, electrode active materials (positive electrode active material and negative electrode active material) play an important role in terms of high output characteristics, safety, and stability. As the electrode active material, the positive electrode active material is typified by a cobalt-based material represented by lithium cobaltate, a spinel manganese-based material, a lithium composite oxide containing nickel, manganese, and cobalt, which is called a ternary system, and lithium iron phosphate. Examples of negative electrode active materials include graphite, titanium, tin, silicon, metal nitride, lithium, and lithium alloys.

  A method for producing a positive electrode active material is generally mixed with a lithium compound, a metal compound, and other materials as raw materials, filled in a container such as a crucible, and heated to several hundred to several hundreds of degrees Celsius for several hours. Manufactured by holding. Although it is mainly produced in an oxidizing atmosphere, it is produced in a reducing atmosphere or an inert atmosphere when producing lithium iron phosphate. However, the method for producing a positive electrode active material requires a heating time, a holding time, and a cooling time for heating regardless of the heating atmosphere, and takes almost one day at the shortest.

  Patent Document 1 describes that by using a specific amorphous cobalt compound as a cobalt source, the temperature required for heating can be lowered and the required time can be shortened. However, the production equipment uses almost the same firing equipment as before, and the production time has not been drastically shortened.

  Patent Document 2 describes three manufacturing methods in which the required time is approximately less than 1 hour. The first is a method called spray pyrolysis. According to this method, an electrode active material for a storage element having good battery characteristics can be produced in about 10 minutes. However, even in continuous operation for about 1 hour, the equipment was blocked by the product, and high-efficiency operation of mass production equipment was difficult.

  The second is a method called microwave heating, which can produce an electrode active material for a storage element with good battery characteristics in about 10 minutes. Microwave heating is characterized in that it can selectively heat an object, but in actuality, a container such as a crucible is filled and heated. Therefore, there is a large temperature distribution in the vicinity of the crucible wall and in the vicinity of the open area, and it has not yet been established as a method for industrially producing products with homogeneous characteristics. In order to solve this drawback, a method of heating the entire furnace has also been proposed (Patent Document 3), but this does not make use of the characteristics of microwave heating.

  The third is heating by a rotary kiln, and this method can produce an electrode active material for a storage element with good battery characteristics in about 10 minutes. However, when the heated cylindrical tube is made of ceramics such as alumina, the upper limit is a tube having a diameter of 200 mm and a length of 2000 mm, so that the productivity of the electrode active material for a storage element is not sufficient.

JP-A-10-279315 JP 2007-230784 A JP 2006-24448 A

  An object of this invention is to provide the manufacturing method of the electrode active material for electrical storage elements which can be manufactured continuously efficiently in a short time.

The present invention has found that the above-mentioned problems can be solved by supplying a raw material component mixture to an irradiation region formed by at least two microwave oscillators and heating it, and has completed the present invention.
That is, this invention provides the manufacturing method of the electrode active material for electrical storage elements which has the following structures.
[1] A microwave heating furnace having at least two inverter-controlled microwave oscillators, wherein each microwave irradiation region is disposed so as to overlap in one region, and is operated in a decoupling state with each other. A method for producing an electrode active material for a storage element, comprising: using a raw material component mixture to supply the irradiation region, and heating the raw material component mixture.
[2] The method for producing an electrode active material for a storage element according to [1], wherein the raw material component mixture is a powder, and the powder is dropped from an upper part of the microwave irradiation region and passed through the irradiation region.

  According to the production method of the present invention, an electrode active material for a storage element that can be continuously produced efficiently in a short time can be obtained.

  The electrode active material for a storage element in the present invention (hereinafter abbreviated as “active material” if necessary) can be applied to almost all electrode active materials for a storage element that require heat treatment. For example, in the case of a lithium ion secondary battery that is a non-aqueous secondary battery, examples of the positive electrode active material include cobalt, nickel, spinel manganese, ternary, and olivine. Examples of the negative electrode active material include graphites, titanium-based, tin-based, silicon-based, metal nitride-based materials, and lithium-based materials such as lithium and lithium alloys. In the case of an alkaline secondary battery, examples of the positive electrode active material include nickel hydroxide and nickel hydroxide combined with nickel hydroxide, and examples of the negative electrode active material include nickel and titanium-based hydrogen storage alloys. Moreover, in the case of the active material for electric double layer capacitors, activated carbon, boron-treated activated carbon, etc. are mentioned.

<Raw material component mixture>
The raw material component mixture in this invention is not specifically limited, The raw material component according to the various active material to manufacture can be included. For example, in the case of LiFePO ₄ which is olivine, LiH ₂ PO ₄ or LiH ₂ PO ₄ aqueous solution can be used as the lithium source and the phosphate source. Especially, it is preferable that all or a part of the raw material components is a solution composed of a common solvent because the raw material components can be homogeneously mixed and a homogeneous product can be produced. Furthermore, it is more preferable that the common solvent is water. In order to precisely control the equivalent of lithium or phosphoric acid, other lithium compounds or phosphoric acid compounds may be used. As other lithium sources and phosphoric acid sources, Li ₂ CO ₃ , Li ₂ O, (NH ₄ ) ₂ HPO ₄ , and NH ₄ H ₂ PO ₄ are preferable because they leave few unnecessary elements in the product. . The raw material component mixture can also be prepared by dissolving a predetermined amount of a lithium compound in an aqueous phosphoric acid solution.

The iron source of LiFePO ₄ may be an iron divalent or trivalent compound, and general iron oxalate or the like can be used as a raw material. From the standpoint is soluble in an aqueous solution of the lithium source and the phosphate source, since it is possible to use an iron salt of an organic acid to the iron source is preferably a very inexpensive and readily available, Fe ₂ O ₃ Iron oxides such as FeOOH and Fe ₃ O ₄ are more preferable. Furthermore, FeOOH, which is an intermediate raw material of synthetic Fe ₂ O ₃ , is particularly preferable because it can be easily refined in a phosphoric acid aqueous solution.
In the case of lithium titanate, which is a negative electrode active material, examples of the raw material component mixture include a mixture of lithium carbonate and titanium oxide.

  The raw material component mixture in the present invention is heated by at least part of the raw material components absorbing microwaves. Although cobalt and cobalt oxide are known to absorb microwaves well, nickel oxides, manganese oxides, iron oxides, silicon-based materials, and the like are difficult to absorb microwaves. However, when using a raw material that hardly absorbs microwaves, such as silicon, it is possible to heat by making the active material finer and combining it with electron conductive carbon that easily absorbs microwaves. Become. In addition, since the silicon-based active material has poor electron conductivity, a large volume change is caused by insertion and extraction of Li due to charge and discharge. In order to increase the electronic conductivity of the silicon-based active material, it is effective to refine the active material, coat the carbon of the refined active material on the surface, and introduce carbon into the active material.

  Furthermore, by using a core-shell type silicon-based active material in which a metal silicon core is coated with a silicon dioxide shell in conjunction with the miniaturization of the active material, it is possible to prevent silicon from collapsing due to a large volume change during charge / discharge it can. Specifically, after synthesizing silicon monoxide from a mixture of silicon dioxide and metal silicon, it is electrochemically active by heat-treating in a microwave heating furnace of the present invention under an inert atmosphere and disproportionating. A core-shell type silicon-based active material in which metallic silicon is dispersed in electrochemically inert silicon dioxide can be produced. With such a structure, it is considered that a large volume change of the silicon-based active material can be suppressed by the silicon dioxide matrix, and the active material can be prevented from collapsing and cycle deterioration to achieve a long life.

  For the refinement of the active material, it is possible to use a method of pulverizing with mechanical impact or pulverizing with a jet mill or the like. However, the active material is dispersed in the aqueous solution of the lithium source and the phosphoric acid source. A method of subjecting the dispersion to refinement is preferable in that mixing and refinement can be performed in one step. There is no particular limitation on the dispersion refinement as long as it is a method of applying a shearing force, but the dispersion can be efficiently refined and the mixing of foreign matters can be controlled at a low level between two rotors with greatly different rotational speeds. A method of miniaturization by passing between two disks or between a rotor and a stator, a method of jetting at a high pressure from a nozzle and colliding with each other or colliding with a shielding object, causing cavitation in the dispersion liquid A method of using a finer method, a bead mill, a planetary ball mill, or a ball mill is preferable.

In the present invention, the preferable particle size in the dispersion of the solid raw material component refined depends on the type of active material and the type of power storage element. For example, in the case of LiFePO ₄ , the median diameter (D50) is preferably 1 μm or less because a homogeneous synthesis reaction can be performed. In the case of a silicon-based active material, the D50 of silicon monoxide is preferably 0.1 to 30 μm. The median diameter (D50) is the median value of the cumulative particle size of all particles, and can be measured by a laser diffraction scattering method.

Various methods for combining an active material and electron conductive carbon have been proposed, and any method may be used. Among them, it is preferable to use a solution of electron conductive carbon or a precursor compound of electron conductive carbon because even a finely divided active material can be uniformly combined. The solvent of the conductive carbon or precursor compound solution is preferably water because it is easy to handle. By mixing the aqueous solution of the electron conductive carbon precursor into the raw material mixture dispersion liquid that has been refined in an aqueous medium, it becomes possible to mix the two together, and finally the electron conductive carbon is homogeneously formed into a fine active material. It is possible to produce an active material that is combined with the active material.
As a precursor of electron-conductive carbon soluble in water, saccharides are preferable because they can be easily converted to electron-conductive carbon by a simple heat treatment, and sucrose and glucose are easily available and inexpensive. More preferred.

  However, it is difficult to obtain a dry powder from an aqueous dispersion containing sucrose or glucose by spray drying. In order to obtain a dry powder from an aqueous dispersion by spray drying, it is effective to use a specific caramel, oligosaccharide, dextrin, water-soluble dietary fiber, water-soluble cellulose degradation product, etc. as the electron conductive carbon precursor. is there. For example, when caramel is used, the caramel is a water-soluble substance that is partially decomposed by heating a saccharide or an aqueous solution of saccharide, partly dehydrated and partly polymerized. It can be interpreted that spray drying is possible as a result of the reduction of the group. Caramel can be used in the present invention, whether it is made of glucose, sucrose, maltose, oligosaccharides or dextrin, or other materials. . These precursors can be dried by spray drying and can be converted to carbon with good electron conductivity by a simple heat treatment like sucrose and oligosaccharides, and are preferably used in the present invention.

  As other saccharides that can be spray-dried, water-soluble dietary fibers and water-soluble cellulose degradation products can be used, and they have at least two hexose units. Among the bonds, the amount of bonds excluding α-1,4 bonds is 20% or more, preferably 30% or more, or the number average molecular weight is 350 or more, preferably 400 to tens of thousands or any two Saccharides that satisfy can be used. For example, cellobiose obtained by decomposing cellulose into a dimer has an average molecular weight of less than 350, but can be spray-dried because the bond of hexose units is a β-bond. It can be used. These saccharides undergo a carbonization reaction by thermal decomposition under substantially the same conditions as sucrose, and the yield of electron conductive carbon is higher than that of sucrose and glucose. If the amount of bonds excluding α-1,4 bonds is less than 20%, spray drying cannot be performed, which is not preferable. On the other hand, if the average molecular weight is less than 350, the —OH group at the end of the molecular chain is increased, the hydrophilicity is increased and spray drying becomes impossible, which is not preferable.

  The raw material component mixture in the present invention is obtained by removing water as a dispersion medium from a finely divided aqueous raw material component dispersion or a dispersion obtained by mixing the dispersion and an aqueous solution of an electron conductive carbon precursor. Prepared by drying. The dry powder can be prepared using various drying processes, but the particle size can be controlled and the preparation of a homogeneous composition powder is easy. It is preferable that the method is dried while feeding. For example, in the case of spray drying, any other method such as a nozzle type, a slit type, a turntable type, or a two-fluid type, a three-fluid type, a four-fluid type, etc. can be used preferably. The drying conditions are determined by the capacity of the equipment to be used, the required particle size, raw material components, and the like. Such conditions are preferable because undesirable side reactions between the raw material components can be suppressed. Thereby, almost all of the raw material components can be recovered, and the particle control of the obtained aggregated particles is easy. The median diameter (D50) of the dried aggregated particles varies depending on the type of active material and the battery system, but D50 is preferably 0.01 to 100 μm, more preferably 0.1 to 30 μm for both the positive electrode and the negative electrode.

  In the production method of the present invention, the composite of the active material and the electron conductive carbon as the conductive auxiliary agent can finely and strongly combine the active material and the conductive auxiliary agent, from the viewpoint of improving the battery characteristics. Is also effective. Therefore, by adding electron conductive carbon to the raw material component mixture and interposing the electron conductive carbon in the active material synthesis process, the electron conductive carbon can be strongly supported on the active material surface or interparticle gaps, It is preferable because battery characteristics are improved.

  Furthermore, in the case of an in-vehicle battery or a large-capacity battery, extremely reliable safety and a long life are required, and a powerful output is also required in a limited volume and mass. In order to realize this powerful output, it is effective to make the active material finer and to apply the electron conductive carbon coating technology to the active material surface.

<Method for producing electrode active material for power storage element>
Using a microwave heating furnace having at least two inverter-controlled microwave oscillators, each microwave irradiation area being overlapped in one area and operating in a decoupled state with each other, The manufacturing method of the present invention is characterized in that the mixture is supplied to the irradiation region and the raw material component mixture is heated. In the manufacturing method according to the present invention, at least two inverter-controlled microwave oscillators have each microwave irradiation region in one region. It is a microwave heating furnace that is overlapped and operated in a decoupled state with each other, and the active material can be synthesized in a very short time by supplying the raw material component mixture to the irradiation zone and heating the raw material component mixture. it can.

  Any microwave oscillator capable of generating microwaves can be used for the microwave heating furnace in the present invention. Among these, a magnetron type generator and a klystron type generator are more preferable from the viewpoint of easy availability. As the magnetron type generator, a 2.45 GHz band magnetron is generally used and can be suitably used in the present invention.

  The microwave heating furnace of the present invention irradiates microwaves by superimposing at least two magnetron type generators controlled by a single mode inverter on a single irradiation area by utilizing the high directivity of microwaves. By arranging in such a way that it can be operated in combination with a power supply device that can be operated in parallel in a decoupled state, one formed irradiation area can produce an output that is the sum of the outputs of each of the multiple units used.

  In general, it is considered difficult to operate a plurality of magnetrons in parallel. However, for example, if three transmitters are arranged symmetrically on three planes with respect to the trihedral symmetry axis of the tetrahedron and are connected to commercial three-phase alternating current, three microwaves having independent electrolytic distributions are each 1 It is possible to concentrate in one region and irradiate each in a decoupled state. Here, the decoupling state refers to a state in which a plurality of magnetrons are simply interlocked to prevent a decrease in output, and can be simultaneously operated while expressing any output controlled in phase angle. . The total output obtained by adding the outputs of the individual transmitters is supplied to the irradiation area thus formed.

  Furthermore, when the primary side of each set is connected in parallel to the basic configuration circuit of three sets of six single-phase AC transformers, one set of two sets, and three-phase AC is input, and the secondary side of each set is connected in series, A 6-phase AC output can be obtained from a 3-phase AC. In this three-phase to six-phase conversion system, star-star connection and delta-star connection are possible, and the two connection methods have a phase difference of 30 degrees. By using this phase difference, it is also possible to directly convert from 3 phases to 12 layers. Therefore, it is possible to operate 12 magnetrons in parallel, and by concentrating 12 microwaves in one irradiation area in a decoupled state, the total output obtained by adding 12 outputs to one It is also possible to irradiate while concentrating on the area.

On the other hand, a plurality of magnetrons are operated in parallel by combining a power distribution unit that can distribute power into a plurality of phases, a phase variable unit that variably controls the output phase of each divided power, and an amplification unit that amplifies the phase-controlled power output. It is also possible. In the present invention, any method capable of operating a plurality of microwave oscillators with their respective phases controlled by any method can be used.
The number of microwave oscillators is preferably 2 to 24 and particularly preferably 3 to 12 in terms of productivity and equipment cost.

The supply method of the raw material component mixture in the present invention is not particularly limited, and can be performed by various methods. Especially, the method of supplying a raw material component mixture directly to an irradiation area is preferable since it can heat uniformly efficiently. Especially, since efficient heating and a homogeneous reaction are possible, it is more preferable to drop a raw material component mixture from the upper part of an irradiation area, to irradiate with microwaves, to heat and to react. Furthermore, it is a method of dropping and irradiating the powder of the raw material component mixture. The method of dropping and irradiating the powder of the raw material component mixture is particularly preferable because rapid heating and rapid cooling after the reaction are possible, and the synthesis reaction can be performed in an extremely short time.
The feed rate of the raw material component mixture varies depending on the output of the microwave heating apparatus and the size of the equipment, but is preferably 1 g / min to 100 kg / min, more preferably 10 g / min to 10 kg / min, and 0.5 kg / min. ˜3 kg / min is particularly preferred.

  The temperature at which the powder of the raw material component mixture is heated by a plurality of microwave oscillators and the irradiation time can be appropriately adjusted depending on the raw material component mixture. For example, when the electron conductive carbon or the electron conductive carbon precursor is compounded, the active material is dispersed in the electron conductive carbon precursor aqueous solution, and then a dry powder is obtained by spray drying or the like. An active material in which electron conductive carbon is combined can also be obtained by carbonizing the carbon precursor.

  The heating temperature is preferably 150 to 350 ° C. since carbonization proceeds at 150 to 1500 ° C., since it can be performed in an air atmosphere. In addition, when the heating temperature is 300 ° C. or higher, carbon burns and disappears in the presence of oxygen. Therefore, the heating is preferably performed in an inert atmosphere such as nitrogen or argon, under reduced pressure in the atmosphere, or in a reducing atmosphere.

In the case of a composite of LiFePO ₄ raw material mixed powder and an electron conductive carbon precursor, synthesis of LiFePO ₄ and carbonization of the precursor are performed in one heating step using the microwave heating furnace in the present invention. be able to. Synthesis of LiFePO ₄ is, 300-1,250 ° C. under inert atmosphere, preferably heat-treated at 350 to 1200 ° C., conversion to the electron conductive carbon synthetic precursor of LiFePO ₄ having an olivine type structure simultaneously proceed . In particular, when the precursor compound is a saccharide, the saccharide functions also as a reducing agent during the synthesis of LiFePO ₄ , and thus is suitable for smoothly spreading the synthesis reaction. When the heating temperature is lower than 300 ° C., the synthesis reaction is difficult to perform, and when it is higher than 1250 ° C., a side reaction product is generated.

  Also in the case of a silicon-based composite of silicon monoxide and an electron conductive carbon precursor, the disproportionation reaction and carbonization of the precursor can be performed in one heating step using the microwave heating furnace in the present invention. it can. The disproportionation of silicon monoxide is performed at 900 to 1500 ° C., preferably 1000 to 1350 ° C., under an inert atmosphere. Synthesis of the core-shell type silicon-based active material composed of silicon and silicon dioxide as the active material and the precursor Conversion to electron conductive carbon is made. In this way, an active material having electron conductive carbon that extends to the surface of the particles and the interface or gap between the small particles can be produced.

The heating time is not generally determined depending on the processing temperature, particle diameter, and particle shape, but is usually preferably 1 second to 48 hours.
Since the production method of the present invention can synthesize an active material in an extremely short time, the synthesis reaction can be performed without causing enlargement or sintering of the active material.

The schematic diagram which observed the microwave heating furnace of this invention from right above. The schematic diagram which observed the microwave heating furnace of this invention from the side. X-ray diffraction pattern diagram of LiFePO ₄ (A) prepared in Example 1. 2 is a particle size distribution diagram of LiFePO ₄ (A) manufactured in Example 1. FIG. FIG. 3 is an SEM diagram of LiFePO ₄ (A) manufactured in Example 1. The X-ray-diffraction pattern figure of the black product (C) manufactured by the comparative example 2. FIG. The arrows in the figure are the main diffraction peaks not attributed to LiFePO ₄ . X-ray diffraction pattern diagram of LiCoO ₂ (D) prepared in Example 2.

The present invention will be described more specifically with reference to the following examples. However, the interpretation of the present invention is not limited by these examples. In the examples, the capacity retention rate of the battery was determined by the following formula.
Capacity retention rate (%) = 100th cycle discharge capacity / initial discharge capacity X100.

[Microwave heating furnace]
The schematic diagram of the microwave heating furnace used in the examples is shown in FIGS. 1 and 2 below. FIG. 1 shows that six 0.5 kW magnetrons are evenly arranged in an irradiation region having a diameter of 3 cm, and single mode microwaves oscillated from the respective magnetrons overlap to form an irradiation region. FIG. 2 shows that each microwave is irradiated from the direction 30 ° above the irradiation region. Each of the six magnetrons is connected to each phase converted from a commercial three-phase alternating current to a six-phase alternating current. On the other hand, a heating furnace connected with only one 1.0 kW magnetron was also prepared for comparison.

[Example 1]
313.1 g of 85 mass% H3PO4 was diluted with 1000 g of pure water. While stirring this phosphoric acid aqueous solution, 100.3 g of Li2CO3 was added and dissolved to obtain an aqueous solution of lithium dihydrogen phosphate. While stirring this aqueous solution, 250.5 g of FeOOH having a molecular weight of 92.2 per equivalent of iron was added, and 400 g of pure water was further added to prepare an aqueous dispersion. This dispersion was refined by a bead mill using zirconia beads having a diameter of 0.1 mm for 1 hour to obtain an aqueous dispersion having a D50 of 0.16 μm. To this aqueous dispersion, 82.9 g of a caramel aqueous solution containing 62% by mass of glucose-derived caramel is added, and an aqueous solution containing a raw material component for synthesizing lithium iron phosphate and a caramel as a precursor of conductive carbon is used. A raw material component mixture dispersion was obtained. Subsequently, the raw material component mixture dispersion was dried using a four-fluid nozzle spray dryer to obtain a raw material component mixture powder having a D50 of 2.9 μm.

Next, the microwave heating furnace of the present invention was replaced with nitrogen gas, and then a nitrogen gas containing 5% by volume of hydrogen was supplied at a flow rate of 0.8 liter / min, while the raw material component mixture powder was 15 g / When the heat treatment was continued for 10 minutes while the temperature of the irradiation region was controlled at 610 ° C., 117.3 g of olivine-type LiFePO ₄ (A) having a D50 of 2.5 μm was obtained. 3, 4, and 5 are an X-ray diffraction pattern diagram, a particle size distribution diagram, and an SEM observation photograph (magnification is 1000 times) of (A), respectively. From the figure, it was confirmed that (A) is LiFePO ₄ having an olivine structure and fine primary particles with good crystallinity.

After weighing 1.2 g of LiFePO ₄ (A), 0.013 g of carboxymethyl cellulose (hereinafter referred to as CMC), 0.067 g of acetylene black, and 1.27 g of water in a plastic tube, the mixture was stirred for 2 minutes with a spindle type homogenizer. 0.039 g of an aqueous emulsion containing 34.5% by mass of a copolymer of propylene and tetrafluoroethylene (hereinafter referred to as PrTFE) and 60.4% by mass of polytetrafluoroethylene (hereinafter referred to as PTFE). 0.089 g of an aqueous emulsion was added and stirred for 2 seconds with the homogenizer to obtain an aqueous paste. The paste was applied to an aluminum foil and dried, then rolled and punched to a predetermined size to obtain a positive electrode plate.

Lead wires were attached to the positive electrode plate and the lithium foil negative electrode plate, respectively, and stored in a stainless steel cell case via a polyolefin-based separator. Subsequently, an electrolyte solution in which 1 mol / liter of lithium hexafluorophosphate was dissolved in a mixed solution of ethylene carbonate and diethylene carbonate was injected to form a model cell.
The battery characteristics of this model cell were evaluated as follows. That is, a charge-discharge measuring instrument was used after receiving until the battery voltage 4.3V at a charging current 0.6 mA / cm ² at 25 ° C., corresponding to the (1.25C rate discharge current 2.0 mA / cm ² )), Charging and discharging were repeated until 2.0 V, and the initial discharge capacity and the discharge capacity after 100 cycles were determined and evaluated. The results are shown in Table 1.

[Comparative Example 1]
A microwave heating furnace connected to only one 1.0 kW magnetron prepared for comparison in place of the microwave heating furnace was used, and the raw material component mixture powder supply rate was changed to 15 g / min and 5 g / min. When the heat treatment was continued for 10 minutes in the same manner as in Example 1 except that it was supplied at a rate, 35.3 g of a black product (B) was obtained. However, an X-ray diffraction pattern diagram of the black product (B) has a diffraction peak that is judged to be an iron oxide or other by-product or an unreacted raw material, and good LiFePO ₄ could not be synthesized.

[Comparative Example 2]
When the heat treatment was continued for 10 minutes in the same manner as in Comparative Example 1 except that the raw material component mixture powder supply rate was changed to 2.5 g / min, 11.5 g of a black product (C) was obtained. The X-ray diffraction pattern diagram of the black product (C) is shown in FIG. 6, but a diffraction peak that is judged to be a by-reactive product or an unreacted raw material remains, and good LiFePO ₄ could not be synthesized. .

[Example 2]
As a result of obtaining and analyzing commercially available CoOOH, it has a cobalt content of 64.4% by mass, is represented by a composition formula of H1.09CoO1.97, and 2θ = 36 to 37 in X-ray diffraction using CuKα as a radiation source. The half width of the diffraction peak around 5 degrees was 2.1. From the patent No. 4224143, it was confirmed that the relationship between the cobalt content and the half width was preferable as a cobalt source for lithium cobalt composite oxide.

A raw material mixture dispersion liquid in which 273.6 g of CoOOH and 111.1 g of Li ₂ CO ₃ are dispersed in 900 g of pure water is caused to collide with each other under high pressure to be refined to reduce the D50 of the solid raw material component to 0 It was crushed until it became 97 μm. Subsequently, this raw material component mixture dispersion was spray-dried in the same manner as in Example 1 to obtain a raw material component mixture powder having a D50 of 3.1 μm.

When the raw material component mixture powder was supplied from the upper part of the microwave heating furnace irradiation area at a rate of 15 g / min and the heat treatment was continued for 10 minutes while controlling the temperature of the irradiation area at 820 ° C., D50 was 2.9 μm. 112.5 g of LiCoO ₂ (D) was obtained. FIG. 7 is an X-ray diffraction pattern diagram of (D).
Table 1 shows the result of producing a positive electrode plate from LiCoO ₂ (D) in the same manner as in Example 1 and evaluating the battery characteristics.

[Example 3]
0.9 mol of nickel oxide prepared by baking nickel carbonate at 700 ° C. for 15 hours in the atmosphere, 0.9 mol of manganese dioxide prepared by baking manganese carbonate at 700 ° C. for 15 hours in the atmosphere, Examples 0.9 mol of CoOOH similar to that used in No. 2 and 0.375 mol of Li ₂ CO ₃ were dispersed in 1.5 kg of pure water and refined with a bead mill in the same manner as in Example 1, followed by a caramel aqueous solution. After adding 50 g, spray drying was performed to obtain a raw material component mixture powder having a D50 of 3.0 μm.

While supplying synthetic air (oxygen to nitrogen volume ratio of 22 to 78) to the microwave heating furnace at a flow rate of 0.8 liter / min, the raw material component mixture powder is supplied at a rate of 15 g / min from the upper part of the irradiation zone. When the heat treatment was continued for 10 minutes while controlling the temperature of the irradiation region at 890 ° C., 112.5 g of lithium (nickel / manganese / cobalt) composite oxide (E) having a D50 of 2.9 μm was obtained. .
Table 1 shows the results of producing a positive electrode plate from lithium (nickel / manganese / cobalt) composite oxide (E) in the same manner as in Example 1 and evaluating the battery characteristics.

[Example 4]
The same caramel aqueous solution 98 g as in Example 1 was diluted with 1200 g of pure water. While stirring this aqueous solution, 480 g of silicon monoxide having a D50 of 0.36 μm was added to obtain an aqueous dispersion. This aqueous dispersion was spray-dried in the same manner as in Example 1 to obtain a raw material component mixture powder having a D50 of 3.6 μm.
Next, after replacing the microwave heating furnace with argon gas, supplying the raw material component mixture powder at a rate of 15 g / min from the upper part of the irradiation area while supplying argon gas at a flow rate of 0.8 liter / min. The heat treatment was continued for 10 minutes while controlling the temperature of 1300 ° C. As a result, a disproportionated silicon-based negative electrode active material (F) having a D50 of 3.4 μm was obtained.

Example except that 0.63 g of silicon-based negative electrode active material (F) and 0.63 g of graphite were used instead of 1.2 g of LiFePO ₄ (A), and 0.067 g of acetylene black was not used. In the same manner as in Example 1, an aqueous paste for electrode coating was prepared. This paste was applied to a copper foil and dried, then rolled and punched to a predetermined size to obtain an electrode plate. Although this silicon-based electrode plate can be used as a negative electrode plate for lithium ion batteries or the like, the evaluation of battery characteristics is performed using a lithium foil as a counter electrode as a negative electrode, and this silicon-based electrode plate is handled as a positive electrode. And evaluated. The results are shown in Table 1.

  INDUSTRIAL APPLICATION This invention can be utilized for manufacture of an electrode active material for electrical storage devices etc., and can produce an electrode active material with a favorable characteristic in a very short time.

1: Irradiation area where microwaves are irradiated in duplicate 2, 3, 4, 5, 6, 7: Magnetron

Claims (2)

  Using a microwave heating furnace having at least two inverter-controlled microwave oscillators, each microwave irradiation region being arranged so as to overlap in one region and operating in a decoupled state with each other, A method for producing an electrode active material for a storage element, comprising supplying a component mixture to the irradiation region and heating the raw material component mixture.   The method for producing an electrode active material for a storage element according to claim 1, wherein the raw material component mixture is a powder, and the powder is dropped from an upper part of the microwave irradiation region to pass through the irradiation region.

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