KR20090112568A - Method for manufacturing layered crystalline material - Google Patents

Abstract

PURPOSE: A method for manufacturing layered crystalline materials is provided to directly produce vanadium pentoxide micro-crystals with layer length of 100nm or less. CONSTITUTION: A method for manufacturing layered crystalline materials comprises the nano-crystalling step of growing crystals with layer length of 100nm or less(S500). In the nano-crystalling step, vanadate and m-ammonium vanadate are heat-treated below predetermined temperature. The m-ammonium vanadate is prepared from soluble vanadate and heat-treated at 500°C or less. The soluble vanadate represents alkali metal salt.

Description

METHODS FOR MANUFACTURING LAYERED CRYSTALLINE MATERIAL}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the technology of layered crystalline materials of vanadium oxide, and is particularly effective for application to positive electrode active materials of lithium ion secondary batteries.

The technique demonstrated below was examined by this inventor at the time of completing this invention, The outline is as follows.

In a lithium ion secondary battery, improvement of a battery characteristic is tried by using the active material which intercalated lithium ion to the positive electrode from the beginning. As such an active material, vanadium pentoxide is promising. As for vanadium pentoxide, for example, as described in WO2008 / 056794, a fine crystal structure having a predetermined layer length was effective as a positive electrode active material.

Such vanadium pentoxide is manufactured through the following manufacturing processes, as described in the said application. That is, vanadium pentoxide is used as a layered crystalline substance for a vanadium source. Lithium sulfide is used as a lithium source. 3,4-ethylenedioxythiophene (EDOT) is also used as the sulfur-containing organic conductive material. These three are suspended in water and heated to reflux. After that, it is filtered and the filtrate is concentrated. After concentration, it is dried in vacuo and ground in a ball mill. By pulverizing and classifying, the powder of layered crystalline substance is obtained. It was found that the material thus obtained can be effectively used as an active material of a positive electrode material.

The layered fine crystal grains of vanadium pentoxide obtained by such a manufacturing method are not obtained independently but are mixed with an amorphous state. That is, in the manufacturing method described in the above application, in particular, by paying attention to a heating temperature, a concentration temperature and the like, the progress of amorphousization is controlled to induce fine crystal particles having a predetermined layer length.

In this application, it has been reported that microcrystalline particles of vanadium pentoxide can greatly improve battery characteristics. However, in the substance manufactured by the manufacturing method so far, an amorphous state and microcrystal grain are mixed. Even if such a substance is used, for example, as an active material of a positive electrode, the mixed state thereof is slightly changed, and therefore it is not possible to accurately measure how much the influence on the characteristic is. That is, the ratio between the microcrystalline particles and the amorphous state could not be determined accurately.

In addition, such an amorphous state is not preferable because it becomes a site where charge and discharge characteristics deteriorate. Moreover, when an amorphous part is mixed, there exists a problem that electrolyte solution hardly penetrates around a microcrystal grain. Therefore, there exists a possibility that the contact efficiency of a fine crystal particle and electrolyte solution may fall, and high cycle characteristics etc. cannot be exhibited.

Therefore, the present inventors thought whether the amorphous state could be reduced as little as possible or eliminated completely. If it can be set as such a state, it can be judged that the characteristic evaluation based on the obtained active material arises from the substance which excluded the amorphous state. It is also conceivable that the effects of the amorphous state can be ignored. That is, it can be considered that it is a characteristic mainly based on the layered crystalline substance which consists of microcrystal grains of vanadium pentoxide.

MEANS TO SOLVE THE PROBLEM This inventor has examined variously about the manufacturing method of the microcrystal grain of vanadium pentoxide whose layer length is less than 100 nm.

In the manufacturing method of the microcrystal grains examined and studied so far, all were using vanadium pentoxide as a raw material. That is, vanadium pentoxide was used as a raw material in order to obtain the fine crystal of the target vanadium pentoxide.

Hereinafter, the fine crystal of vanadium oxide, such as vanadium pentoxide whose layer length is 100 nm or less, is called fine polycrystalline vanadium. In this specification, it may be simply referred to as nano vanadium below.

It is understandable on a laboratory scale, but this method is very inadequate when considered at the actual industrial scale of manufacture. That is, in the conventional manufacturing method which this inventor examined, the vanadium pentoxide which has larger crystal structure than nano vanadium was used as a raw material. After dissolving it, it recrystallized and obtained vanadium pentoxide (nano vanadium) of the microcrystal structure smaller than the crystal structure of a raw material. However, the present inventors thought that this manufacturing method might have double labor.

That is, vanadium pentoxide used as a raw material is manufactured through the crystallization process. The crystals are dissolved and fine crystals are formed through a crystallization step. In other words, the crystallization process is performed twice. Of course, the content of the crystallization step is different. However, it is considered to be the same in terms of crystallization.

At present, it is convenient to use commercially available crystals of vanadium pentoxide as a method for producing fine crystal particles of vanadium pentoxide which is nano vanadium. However, available vanadium pentoxide is not microcrystals of nano vanadium having a layer length of 100 nm or less. The layer length of the crystal structure is larger than that. In the future, the inventors have thought that if the demand for the fine crystal particles of vanadium pentoxide increases, the double crystallization step in the production method will be an obstacle.

In fact, the raw material crystal of vanadium pentoxide currently available and the fine crystal of vanadium pentoxide which is the final nano vanadium differ in the layer length of the layered crystal structure. Then, the raw material crystal | crystallization of the vanadium pentoxide currently obtained may be large crystal from the beginning. From the beginning, the present inventors thought that what is necessary is just to make fine crystallization of the target nano vanadium size. Therefore, the present inventor thought, for example, whether the microcrystal structure having a layer length of 100 nm or less can be produced directly.

If it can be done, the trouble of obtaining the vanadium pentoxide of a microcrystal grain by recrystallizing using the crystal | crystallization of vanadium pentoxide which is a raw material so far can be eliminated completely. That is, in manufacture of vanadium pentoxide of a microcrystal grain, a process can be reduced remarkably compared with the conventional method which this inventor examined. In addition, the manufacturing cost can be reduced.

In addition, it was thought that such a fine crystallization method of vanadium pentoxide which is nano vanadium is preferable if it can be connected with the manufacturing method of the raw material of vanadium pentoxide which has a layer length longer than nano vanadium. That is, if it can be connected with the conventional manufacturing method, it is possible to follow at least some facilities, apparatuses, etc. of the conventional manufacturing method as it is. By doing so, it was thought that the switch from the conventional manufacturing method to the manufacturing method according to the present invention can also be performed very smoothly and quickly.

An object of the present invention is to efficiently produce fine crystals of vanadium pentoxide having a layer length of 100 nm or less.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

Among the inventions disclosed herein, an outline of representative ones will be briefly described as follows.

By crystal growth in a nanocrystallization process including the step of heat-treating vanadate at a predetermined temperature or less, fine crystals of 100 nm or less in which the layer length does not contain 0 nm are produced.

Among the inventions disclosed herein, the effects obtained by the representative ones are briefly described as follows.

In the present invention, unlike the prior art, fine crystals of vanadium pentoxide of 100 nm or less without a layer length of 0 nm can be directly produced without using vanadium pentoxide having a larger crystal structure than nano vanadium as a raw material. . Therefore, vanadium pentoxide, which is nano vanadium of fine crystal grains, can be supplied at low cost to the field of a power storage device used for an electrode material or the like.

Moreover, this invention is a technique manufactured via vanadate or ammonium metavanadate. Therefore, it can be linked with the conventional manufacturing method which generate | occur | produces vanadate or ammonium metavanadate in between. Thereby, some existing facilities etc. can be followed, and switching to the manufacturing method of this invention can be performed quickly.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail based on drawing. In addition, in all the drawings for demonstrating embodiment, the same code | symbol is attached | subjected to the same member as a principle, and the repeated description is abbreviate | omitted.

The present invention relates to an electrode material. A layered crystalline material usable for an electrode. Such a layered crystalline substance is one having fine crystal particles of vanadium oxide having a layer length larger than 0 nm and 100 nm or less. Hereinafter, as mentioned above, the microcrystal of vanadium oxide, such as vanadium pentoxide whose layer length is 100 nm or less, may only be called nano vanadium.

For example, as such microcrystal grains, the microcrystal grains of vanadium pentoxide which is nano vanadium are mentioned. Such a material can be effectively used, for example, as a positive electrode active material of a power storage device. The interlayer of a microcrystal structure can be used effectively as an active material which is easy to dope and dedope lithium ion. It can be used effectively in a lithium ion secondary battery.

In addition, "layer length" in this specification means the length of the layer in layered crystal structure. For example, it does not interfere even if it is represented by the average diameter of a primary particle judged by electron microscopy or X-ray diffraction analysis.

In addition, in this specification, doping means occlusion, support, adsorption, insertion, etc., and means the state which lithium ion, anion, etc. enter with respect to a positive electrode active material or a negative electrode active material. De-doping means release, desorption, etc., and means the state which lithium ion, anion, etc. come out from a positive electrode active material or a negative electrode active material.

The present invention is characterized in that it can be linked with a conventional manufacturing method. That is, it is a manufacturing technique which can use a part of the conventional manufacturing method. By adopting such a configuration, as described above, the embodiment of the present invention can be quickly performed.

As the vanadium, ore having a high quality alone is not known. As vanadium-containing titanium magnetite, etc., it is by-produced at the time of collection of another metal. In addition, the mountain range is ubiquitous in some parts of the world. Moreover, since it is contained in many crude oils, a combustion material can be used as a raw material. As for such vanadium, Japanese demand is fully supplied by imports. At the time of import, it is traded as ferro vanadium, vanadium pentoxide, etc.

Then, this inventor paid attention to this vanadium pentoxide, and examined the conventional manufacturing method. Among them, attention was paid to a method of producing vanadium pentoxide using a combustion material as a raw material. The manufacturing method is comprised through several processes. Among them, it was found that the specific vanadium compound became the key. Thus, if the specific vanadium compound can be used as a raw material to produce fine crystal particles of vanadium pentoxide, it may be associated with a conventional production method.

The specific vanadium compound is vanadate and ammonium metavanadate (same as ammonium vanadate). In the conventional manufacturing method, vanadium is extracted as vanadium salt from the aqueous solution of the roasted combustion material. The solid of ammonium metavanadate is extracted by salting out of the vanadate extracted in this way. Then, ammonium metavanadate is heated at 600 degreeC or more, ammonium is detached and vanadium pentoxide is manufactured.

Therefore, the present inventors paid attention to ammonium metavanadate, which occurs at the bottom of the manufacturing process. That is, it examined whether the microcrystal of vanadium pentoxide which is nano vanadium cannot be manufactured from ammonium metavanadate. As a result of earnest examination, it discovered that microcrystal grains can be manufactured by controlling temperature this time.

In one aspect of the present invention, a fine crystal of vanadium pentoxide is obtained by heat-treating ammonium metavanadate at a predetermined temperature. That is, for the first time, a microcrystalline structure of nanovanadium is obtained by heat-treating ammonium metavanadate at a predetermined temperature, and the present application is made as described above.

Microcrystal of vanadium pentoxide which is nano vanadium can be manufactured by heating ammonium metavanadate to 100 degreeC or more, More preferably, it is 150 degreeC or more. 150 degreeC or more is preferable at the point which can be almost completely microcrystallized. In addition, the upper limit of heating temperature is 500 degreeC in the present study. That is, microcrystal grains of vanadium pentoxide can be obtained by heating to 100 degreeC or more and 500 degrees C or less. Or it was found for the first time that the microcrystal particle of vanadium pentoxide can be manufactured by heat-processing to 150 degreeC or more and 500 degrees C or less.

In the heat treatment at such a temperature, fine crystals of vanadium pentoxide are possible, for example, if the temperature increase rate is 0.5 ° C / minute or more and 30 ° C / minute or less. This was confirmed by this experiment. If it is less than 0.5 DEG C / min, it takes too much time and is not practical. On the other hand, when it exceeds 30 degreeC / min, a temperature increase rate will become too fast and it will be easy to cause coarsening of a crystal | crystallization.

Even in the range of 0.5 degrees C / min or more and 30 degrees C / min or less, More preferably, it is the range of 1 degrees C / min or more and 10 degrees C / min or less. From the viewpoint of the practicability of production efficiency, it is preferable that it is 3 degrees C / min or more. Moreover, if it is 30 degrees C / min or less, since the layer length of the crystal structure contained in microcrystal | crystallization can be suppressed to 100 nm or less in the state near 100% or 100%, it is preferable.

When the target temperature is reached at the temperature increase rate, it is preferable to maintain the temperature. It is because there exists a possibility that it may fall short of predetermined | prescribed layer length. However, when the temperature increase rate is slowed down, it does not have to be maintained at the target temperature. Rather, in order to avoid the occurrence of crystal growth of a layer length larger than a predetermined value, the holding time may be eliminated. Regarding the retention at the target temperature, the obtained crystal may be sampled, and the crystal state may be grasped and appropriately judged.

In addition, after manufacturing the fine crystal particle of vanadium pentoxide as said point, what is necessary is just to cool slowly. Naturally, the method such as lowering to room temperature is good. Sudden drop in temperature is estimated to cause a change in crystal structure.

Thus, adjustment of the layer length of a microcrystal can be performed by changing temperature conditions as mentioned above. Thus, nanovanadium of optimal layer length can be produced.

In addition, in experiment, it was performed in the range whose oxygen partial pressure is 0% or more and 100% or less. In addition, as heat processing atmosphere, it performed in rare gas atmosphere, such as oxygen atmosphere, argon (Ar), and helium (He).

Using such ammonium metavanadate as a starting material, for example, as described above, in the method of heat treatment at 150 ° C or more and 500 ° C or less, fine crystals of vanadium pentoxide having a layer length of 100 nm or less can be produced directly.

Ammonium metavanadate in the present invention, as described above, occurs in the middle of a conventionally known manufacturing method. In particular, since vanadium is largely contained in crude oil, the combustion material of crude oil is used as a raw material for production of vanadium. The combustion material is roasted, and the alkali metal vanadate alkali metal salt is once extracted from the aqueous solution. In addition, soluble alkali metal vanadate salts are salted to obtain ammonium vanadate.

For example, the combustion residue of a boiler, etc. are roasted, and sodium vanadate is extracted once from the sodium aqueous solution. When the aqueous solution of such soluble sodium vanadate is salted with an ammonia compound, ammonium vanadate is obtained.

1 (a), 1 (b), 1 (c), and 2 show the flowchart of the method for producing nanovanadium in the present invention. That is, in step S100 of FIG. 1A, a combustion material is prepared. For example, as shown to step S110 of FIG. 2, what is necessary is just to prepare the combustion residue of a boiler. Thereafter, the combustion material prepared in step S200 is roasted. For example, in step S210, the combustion residue of the boiler is roasted at 700 ° C to 850 ° C.

In step S300 shown in Fig. 1A, vanadium is extracted from the aqueous solution of roasted ash as vanadium salts such as soluble alkali metal vanadate. For example, as shown in step S310 of FIG. 2, vanadium is extracted as soluble sodium vanadate.

In addition, this invention can also use the soluble vanadate in step S300a as a starting material, as shown to FIG. 1 (b).

In addition, as a vanadate here, for example, VO ₄ ^3- , V ₂ O ₇ ^4- , V ₁₀ O ₂₈ ^6- , V ₄ O ₁₂ ^4- , V ₃ O ₉ ^3- , HVO ₄ ^2- , H ₂ VO ^{_{4 -, HV 10 O 28 5-}} , not a H ₂ V ₁₀ O ₂₈ ^4- matter even be combined with cationic ion. Examples of the cation include sodium, ammonium, potassium, cesium, rubidium, silver, alkylammonium and the like. Specific examples of the vanadate include sodium metavanadate (same as sodium vanadate) in addition to the ammonium metavanadate described in the present embodiment. That is, sodium metavanadate and other vanadium salts can be used in addition to the ammonium metavanadate used in the examples described later.

Thereafter, as shown in Figs. 1A and 1B, in step S400 and step S400a, for example, ammonium metavanadate is salted out from the soluble vanadium acid alkali metal salt. For example, as shown in step S410 of FIG. 2, ammonium hydroxide may be added to the aqueous solution of sodium vanadate to salt the ammonium metavanadate.

In addition, the present invention may further use ammonium metavanadate in step S400b as a starting material, as shown in Fig. 1C.

As shown to step S500, S500a, S500b of FIG.1 (a), FIG.1 (b), FIG.1 (c), a nanocrystallization process is performed after that. That is, as shown to step S510 of FIG. 2, what is necessary is just to heat and process it to 150 degreeC or more and 500 degrees C or less, for example.

As shown in Figs. 1A, 1B, 1C, and 2, steps S600, S600a, S600b and S610, nano vanadium is obtained. That is, nano vanadium which is a microcrystal of vanadium pentoxide having a layer length of 100 nm or less which does not contain 0 nm is obtained.

In addition, at the time of such heating, a temperature increase rate is performed at 0.5 degrees C / min or more and 30 degrees C / min or less, for example. If it is less than 0.5 degree-C / min, it becomes very late and takes time from a standpoint of actual production. If it exceeds 30 ° C / min, the rate of temperature rise becomes too fast, resulting in coarsening of the crystal. More preferably, it is 1 degrees C / min or more and 10 degrees C / min or less. Such a temperature increase rate may basically be performed slowly. It is preferable to perform slowly within the process time at an actual manufacturing site.

In addition, these temperature raising operations can achieve a predetermined purpose even if the time required for the whole is shortened by increasing the temperature increase rate to a temperature region lower than the target temperature and reducing the speed in the vicinity of the target temperature.

When the heat treatment reaches the target temperature of 100 ° C. or higher and 500 ° C. or lower, as described above, the heat treatment may be determined based on the crystal state, and may be appropriately set to hold the time including no retention time.

The state of the layered crystal grains of the nano vanadium obtained in the steps S600, S600a, S600b, and S610 is schematically illustrated in FIG. 3A. In FIG.3 (a), the state which looked at the state of the three-dimensional microcrystal from the cross section is shown. The layered fine crystal grains of vanadium pentoxide which is nano vanadium abbreviated as circular. In this circle, in parallel, the layer state is indicated. In addition, as shown in FIG.3 (b), the microcrystal grain of vanadium pentoxide which is each nano vanadium is 100 nm or less whose layer length does not contain 0 nm, for example.

The presence of such nanovanadium can be verified using, for example, a cross-sectional photograph such as SEM. In the present invention, as the average abundance ratio of the layered crystalline particles having the layer length of 100 nm or less, for example, at least 95% or more, it is currently considered that there is no problem in cycle performance.

As schematically shown in Fig. 3A, a space is formed between the layered crystalline particles, and the electrolyte solution easily penetrates by that much. Therefore, when used as an active material of the electrode, the contact efficiency between the fine layered crystalline particles and the electrolyte is increased, resulting in high cycleability.

By using the nano vanadium prepared in steps S600, S600a, S600b, and S610, for example, electrodes of power storage devices such as batteries can be manufactured. That is, according to the manufacturing method of this invention illustrated in FIG. 1 (a), FIG. 1 (b), FIG. 1 (c), FIG. 2, etc., the layer shape of the large vanadium pentoxide which has a layer length of 100 nm or more at least. Nanovanadium can be obtained without using a crystalline substance as a raw material. A vanadium pentoxide of nano vanadium, which is a layered crystalline material having a layer length of 100 nm or less, can be obtained. Such a layered crystalline substance of nanovanadium can be effectively used as an electrode material of a power storage device such as a battery.

Conventionally, unlike the present invention, for example, nano vanadium has been produced by a flowchart as shown in FIG. 4. That is, in step S1000, a combustion material such as a combustion residue of the boiler is prepared. In step S2000, roasting of the prepared combustion material is performed. In step S3000, vanadium is extracted as an alkali metal salt of vanadium acid, such as soluble sodium vanadate. In step S4000, ammonium metavanadate is obtained by salting out with ammonium hydroxide or the like. In step S5000, the obtained ammonium metavanadate is heated, for example, at 600 degreeC or more, and heat processing is performed. In step S6000, crystals of vanadium pentoxide having a layer length of at least greater than 100 nm are obtained.

Subsequently, nanovanadium, which is a fine crystal of vanadium pentoxide, is produced using the vanadium pentoxide crystalline having a layer length of greater than 100 nm as a raw material.

That is, in step S7100, the vanadium pentoxide obtained in step S6000 and a plurality of lithium raw materials such as lithium sulfide and lithium hydroxide are suspended with water. In step S7200, the mixture is heated to reflux in an inert gas atmosphere. In step S7300, the heated and refluxed suspension is filtered. In step S7400 the filtrate is dried by spray drying or the like. The dried thing in step S7500 is pulverized, and then classified. In step S7600, a heat treatment is carried out to that obtained in step S7500 to perform nanovanadium vanadium pentoxide.

Thus, in the conventional manufacturing method, vanadium pentoxide which has a layer length larger than 100 nm is manufactured once. Furthermore, the fine crystal grains of nano vanadium vanadium pentoxide having a layer length of 100 nm or less were recrystallized through a process such as dissolving it in water again.

However, as illustrated in Fig. 1 (a), Fig. 1 (b), Fig. 1 (c), and Fig. 2, in the manufacturing method of the present invention, as compared with the conventional method shown in Fig. 4, The process can be remarkably shortened. For example, in the present invention, the steps S7100 to S7600 are completely eliminated by changing the steps S1000 to S6000 surrounded by the broken lines in FIG. 4 to the steps S110 to S610 surrounded by the broken lines in FIG.

The nano vanadium obtained by such a manufacturing method of this invention can be used as an electrode material of an electrical storage device. That is, for example, it can be used as an active material of a positive electrode of a lithium ion secondary battery of a power storage device.

The lithium ion secondary battery 10 as a power storage device has a structure as shown in FIG. 5, for example. That is, in the lithium ion secondary battery 10, the negative electrode 11 and the positive electrode 12 are alternately laminated via the separator 13. The outermost layer side is comprised by the cathode 11 in the laminated unit laminated | stacked in multiple times. That is, the structure in which the positive electrode 12 and the negative electrode 11 were laminated | stacked through the separator 13 between the both negative electrodes 11 is inserted, and the electrode unit is comprised.

Moreover, the lithium electrode 14 is provided in the outer side of outermost layer so that the negative electrode 11 arrange | positioned at outermost layer may face. In the lithium electrode 14, for example, metallic lithium 14a is provided to have a predetermined layer thickness on the current collector 14b. In the current collector 14b, holes are formed to form a porous body. The lithium ions eluted from the lithium electrode 14 are predoped to the cathode 11.

The negative electrode 11 constituting the electrode unit is also configured to have a negative electrode active material 11a provided with a predetermined thickness on the current collector 11b. The electrical power collector 11b is comprised from the porous body which perforated. The positive electrode 12 is also provided with a positive electrode active material 12a with a predetermined thickness on the current collector 12b. The current collector 12b is formed of a porous body with holes.

The electrode unit of such a structure is immersed in electrolyte solution, and the lithium ion secondary battery 10 is comprised.

The said negative electrode active material and the positive electrode active material are mixed with water, a binder, an electroconductive aid, etc., respectively, and are comprised from a slurry. The active material formed from such a slurry is coated on each current collector with a predetermined layer thickness by, for example, a die coater or the like. After that, the positive electrode 11 and the positive electrode 12 as positive electrodes 12 are manufactured.

As an active material for negative electrodes, the following can be used, for example. That is, a lithium intercalation carbon material etc. are mentioned in a non-aqueous lithium ion secondary battery. For example, graphite, carbon-based materials, polyacene-based materials and the like can be used. Examples of the carbon-based material include hardly graphitized carbon materials. As a polyacene substance, PAS etc. which are an insoluble infusible substrate which has a polyacene type frame | skeleton are mentioned, for example. All of these negative electrode active materials are materials which can reversibly dope lithium ions.

In the case of using a carbon material capable of doping or dedoping lithium ions or the like, by separately providing a lithium electrode, lithium ions are predoped from the lithium electrode to the cathode during initial charging. As a lithium ion source, metal lithium, a lithium-aluminum alloy, etc. can be used. That is, it can use if it is a substance which contains lithium element at least and can supply lithium ion.

As a positive electrode active material, the layered crystalline substance of vanadium pentoxide which is nano vanadium manufactured by the manufacturing method of this invention is used. For example, it is used as an electrode material for positive electrodes of the non-aqueous lithium secondary battery shown in FIG. The lithium ions are preferably doped in a molar ratio of 0.1 to 6 with respect to the metal oxide of vanadium pentoxide. If the doping amount of the lithium ions is less than 0.1 in a molar ratio, the doping effect is not sufficiently exhibited. On the other hand, if the doping amount of the lithium ions exceeds 6, the metal oxide may be reduced to the metal, which is not preferable.

As the binder, polyvinylidene fluoride (PVDF) or the like can be used. Such a binder is preferably mixed with the conductive particles described below to form a slurry. An electrode can be formed by apply | coating such a slurry to predetermined | prescribed layer thickness on the electrically conductive substrate which is an electrical power collector demonstrated below.

In addition, as the said electroconductive assistant, the following electroconductive particle can be used, for example. That is, metals, such as conductive carbon, such as Ketjen Black, copper, iron, silver, nickel, palladium, gold, platinum, indium, tungsten, conductive metal oxides, such as indium oxide and tin oxide, etc. are mentioned. Such electroconductive particle should just be contained in the ratio of 1 to 30% of the weight of the said metal oxide, for example.

In addition, a lithium alloy can also be used as a lithium electrode instead of the metallic lithium mentioned above. For example, lithium type metal materials, such as a Li-Al alloy, are mentioned. Intermetallic compound materials of metals such as tin and silicon and lithium metals, and lithium compounds such as lithium nitride.

In addition, for example, a conductive substrate exhibiting conductivity on at least the surface of the current collector in contact with the active material of the positive electrode and the negative electrode is used. As such a substrate, a conductive material such as a metal, a conductive metal oxide, or conductive carbon can be used. In particular, what is necessary is just to form with copper, gold, aluminum, these alloys, or conductive carbon. In the case where the substrate is formed of a non-conductive material, the substrate can be used by covering the substrate with a conductive material.

The following non-aqueous solvent can be used for electrolyte solution which immerses the laminated unit of the said structure, for example. That is, as a non-aqueous solvent, linear carbonate, cyclic carbonate, cyclic ester, a nitrile compound, an acid anhydride, an amide compound, a phosphate compound, an amine compound, etc. are mentioned. Specific examples of the non-aqueous solvent include ethylene carbonate, diethyl carbonate (DEC), propylene carbonate, dimethoxyethane, γ-butyrolactone, n-methylpyrrolidinone, N, N'-dimethylacetamide, Acetonitrile or a mixture of propylene carbonate and dimethoxyethane, a mixture of sulfolane and tetrahydrofuran, and the like.

As the electrolyte dissolved in such an electrolyte solution, for example, the following can be used. That is, lithium electrolytes such as CF ₃ SO ₃ Li, C ₄ F ₉ SO ₈ Li, (CF ₃ SO ₂ ) ₂ NLi, (CF ₃ SO ₂ ) ₃ CLi, LiBF ₄ , LiPF ₆ , and LiClO ₄ are used. Can be used. The solvent which dissolves this electrolyte is a non-aqueous solvent. The electrolyte layer interposed between the positive electrode and the negative electrode may be a polymer gel (polymer gel electrolyte) containing a nonaqueous solution of the electrolyte. Since vanadium pentoxide of the layered crystalline substance is dissolved in water, it is required to use a nonaqueous solvent as described above.

<Example>

[Production of anode]

In this example, fine crystals of vanadium pentoxide were produced by nanocrystallization using ammonium metavanadate as a raw material. For example, 10 g of ammonium metavanadate (manufactured by Kanto Chemical Co., Ltd.) was set to a target temperature at a temperature increase rate of 5 ° C / min using an electric furnace controlled by a program controller with a PID control function. In experiment, target temperature was 150 degreeC (Example 1 in a figure), 180 degreeC (Example 2 in a figure), 200 degreeC (Example 3 in a figure), 400 degreeC (Example 4 in a figure) And 500 degreeC (Example 5 in drawing), respectively, and the microcrystal of vanadium pentoxide which is nano vanadium was obtained.

These target temperatures were maintained for 0.6 hours each. Thereafter, it was left to stand at room temperature. It carried out in 20% of oxygen partial pressure and oxygen atmosphere. As a result, in each of them, vanadium pentoxide of fine crystal grains having a layer length of 100 nm or less was obtained.

90 wt% of the layered crystalline material which is the microcrystalline particles of the vanadium pentoxide of Examples 1 to 5 thus obtained was mixed with 5 wt% of conductive carbon black and 5 wt% of polyvinylidene fluoride (PVDF), and the solvent As a slurry, N-methylpyrrolidone (NMP) was used. This slurry was coated on the porous Al foil by the doctor blade method. A uniform coating was applied to both surfaces or one surface of the copper current collector having through holes so that the mixture density per side was 2 g / cm 3, and cut into a 24 mm x 36 mm square to form an anode. .

[Production of negative electrode]

Graphite and PVDF as a binder were mixed in a weight ratio of 94: 6 to prepare a slurry diluted with NMP. The slurry was uniformly coated on both sides or one side of a copper current collector having through holes so as to have a mixture density of 1.7 mg / cm 3 per side, and cut into a 26 mm x 38 mm square to form a negative electrode.

[Production of battery]

Twelve positive electrodes and 13 negative electrodes (two coated on one side) prepared as described above were laminated through a polyolefin-based microporous membrane as a separator. Furthermore, a lithium pole bonded with metal lithium to a stainless steel porous foil was disposed on the outermost layer via a separator, to produce a three-pole laminated unit consisting of a positive electrode, a negative electrode, a lithium electrode, and a separator. The tripolar lamination unit was packaged in an aluminum laminate film, and an electrolyte solution of ethylene carbonate (EC) / diethyl carbonate (DEC) = 1/3 (weight ratio) in which lithium borofluoride was dissolved at 1 mol / L. Was injected.

[Measurement of Capacity Degradation Rate]

After each battery in Examples 1-5 produced as mentioned above was left to stand for 20 days, each 1 cell was disassembled. Since all of the metallic lithium disappeared completely, it was confirmed that the required amount of lithium ions were previously stored on the negative electrode, i.e., pre-doped.

Moreover, the charge / discharge cycle test was done using the remaining 1 cell of cells. Charging was performed by a constant current-constant voltage (CC-CV) charging method of 4.1 V at 0.1 C. As such a charging method, a method of terminating at the time when 30 hours has elapsed is adopted. Discharge was made into the constant current (CC) discharge system which is complete | finished when it became 1.35V at 0.05C. The capacity deterioration rate was calculated as a percentage of the discharge capacity immediately before the discharge capacity.

The measurement results are shown in Figs. 6A and 6B. As shown to Fig.6 (a) and FIG.6 (b), the value represented by capacity | capacitance deterioration rate (-Q (mAh / g active material) / cycle) at 150 degreeC was 1.6. Similarly, when the fine crystal of vanadium pentoxide obtained at 180 degreeC, 200 degreeC, 400 degreeC, and 500 degreeC was used, it became 1.5, 1.4, 2, 3. Very low capacity deterioration rate could be suppressed.

In the above, invention made by this inventor was concretely demonstrated based on embodiment. However, the present invention is not limited to the above embodiment. Of course, it can be variously changed without departing from the gist.

This invention can be used especially effectively in the positive electrode field of a lithium ion secondary battery.

1 (a), 1 (b), and 1 (c) are flowcharts showing an embodiment of a manufacturing method according to the present invention, respectively.

2 is a flowchart illustrating an embodiment of a manufacturing method according to the present invention.

FIG. 3A is an explanatory diagram schematically showing the crystal structure of the nano vanadium produced by the production method according to the present invention, and FIG. 3B is a schematic diagram illustrating the layer length of the nano vanadium.

4 is a flowchart showing an example of a conventional manufacturing method.

5 is an explanatory diagram schematically showing an example of a power storage device.

6 (a) and 6 (b) are explanatory diagrams showing the relationship between the heat treatment and the capacity deterioration rate.

<Explanation of symbols for the main parts of the drawings>

10: lithium ion secondary battery 11: negative electrode

11a: active material 11b: current collector

12: positive electrode 12a: active material

12b: Current collector 13: Separator

14: lithium electrode 14a: metal lithium

Claims (9)

A method for producing a layered crystalline material of fine crystals of vanadium oxide having a layer length of 100 nm or less that does not contain 0 nm, A nanocrystallization process for crystal growth such that the layer length is 100 nm or less, The nanocrystallization step, the method of producing a layered crystalline material, characterized in that it comprises a step of heat-treating vanadate salt at a predetermined temperature or less. The method for producing a layered crystalline material according to claim 1, wherein the nanocrystallization step includes a step of heat-treating ammonium metavanadate at 500 ° C or lower. The method for producing a layered crystalline material according to claim 2, wherein the ammonium metavanadate is heat treated at 150 ° C or higher. The method for producing a layered crystalline material according to claim 2 or 3, wherein the ammonium metavanadate is produced by salting out of soluble vanadate. The said soluble vanadate is a salt of an alkali metal, The manufacturing method of the layered crystalline material of Claim 4 characterized by the above-mentioned. The method for producing a layered crystalline material according to claim 5, wherein the soluble vanadate is sodium salt. The method for producing a layered crystalline material according to claim 4, wherein the soluble vanadate is produced using a combustion material as a raw material. The method for producing a layered crystalline material according to any one of claims 1 to 3, wherein the 100 nm or less fine crystal whose layer length does not contain 0 nm is used for the electrode of the electrical storage device. The method for producing a layered crystalline material according to claim 8, wherein the power storage device is a lithium ion secondary battery.

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