JP6124062B2 - Positive electrode material for power storage device and method for producing the same - Google Patents

Description

  The present invention relates to a positive electrode material for an electricity storage device (hereinafter also simply referred to as “positive electrode material”) used for portable electronic devices, electric vehicles, and the like, and a method for manufacturing the same.

Lithium ion secondary batteries have established themselves as high-capacity and lightweight power supplies that are indispensable for portable electronic terminals and electric vehicles. Conventionally, inorganic metal oxides such as lithium cobaltate (LiCoO ₂ ) and lithium manganate (LiMn ₂ O ₄ ) have been used as positive electrode materials for lithium ion secondary batteries. However, with the recent increase in power consumption due to higher performance of electronic devices, further increase in capacity of lithium ion secondary batteries is required.

In recent years, a positive electrode material made of a polyanion compound such as LiFePO ₄ has attracted attention because it is advantageous in terms of cost, resources, and the like, and various researches and developments are underway.

JP-A-9-134725

A polyanionic positive electrode material such as LiFePO ₄ has a very large internal resistance compared to a lithium metal oxide such as LiCoO ₂ , so that resistance polarization increases during charge / discharge, and it is difficult to obtain a sufficient discharge capacity. There is a problem.

  As a method for solving such a problem, a method has been proposed in which a polyanionic positive electrode active material is pulverized to increase the specific surface area to facilitate the diffusion of lithium ions and reduce the internal resistance. Alternatively, it has been proposed that a carbon source such as an organic compound is mixed with a polyanionic positive electrode active material powder and fired to form a carbon-containing layer on the surface of the positive electrode active material. However, if the particle size of the positive electrode active material powder is small, the surface area becomes large, and a large amount of carbon source is required to form a uniform carbon-containing layer on the entire surface, and the surface is homogeneous. There was a problem that it was difficult to coat. Moreover, when the ratio of the amount of carbon remaining after firing with respect to the amount of added carbon of the carbon source to be mixed is low, the thickness of the carbon-containing layer formed on the surface tends to be uneven. As a result, there is a problem that a desired discharge capacity cannot be obtained because the movement of lithium ions is hindered in a place where the thickness of the carbon-containing layer is large.

  In view of the above problems, the present invention provides a method for producing a positive electrode material for an electricity storage device having a high discharge capacity by increasing the ratio of the amount of carbon remaining after firing relative to the amount of carbon added to the carbon source to be mixed. The purpose is to do.

  The method for producing a positive electrode material for an electricity storage device according to the present invention includes (1) an inorganic powder containing at least one element selected from Li and Na, at least one element selected from Si, P, Al and B, and O And (2) forming a carbon-containing layer on the surface of the inorganic powder by heat-treating the mixture.

  It is preferable that the said process (2) precipitates the crystal | crystallization containing a polyanion compound while forming a carbon containing layer in the inorganic powder surface.

The inorganic powder is expressed in mol% in terms of oxide, Li ₂ O + Na ₂ O 10-50%, MnO ₂ + CoO + NiO + Fe ₂ O ₃ 20-65% and SiO ₂ + P ₂ O ₅ + Al ₂ O ₃ + B ₂ O ₃ 10 It is preferable to contain -50%.

  The inorganic powder is produced by a method including (0-a) a step of melting and vitrifying the raw material powder, and (0-b) a step of pulverizing the molten glass after molding. preferable.

  The inorganic powder is preferably a crystalline glass powder or a crystallized glass powder.

  The inorganic powder preferably has an average particle size of 1.8 μm or less.

  The saponification degree of the polyvinyl alcohol resin is preferably 70 to 99%.

  The degree of polymerization of the polyvinyl alcohol resin is preferably 100 to 1000.

  The positive electrode material for an electricity storage device of the present invention is manufactured by any one of the methods described above.

  The positive electrode material for an electricity storage device of the present invention preferably has a carbon content of 0.01 to 20% by mass.

  According to the present invention, since the ratio of the carbon content remaining after firing to the added carbon content of the carbon source to be mixed can be increased, a positive electrode material for an electricity storage device having a high discharge capacity can be produced.

  The method for producing a positive electrode material for an electricity storage device according to the present invention includes (1) an inorganic powder containing at least one element selected from Li and Na, at least one element selected from Si, P, Al and B, and O And (2) a step of forming a carbon-containing layer on the surface of the inorganic powder by heat-treating the mixture.

  By mixing and heat-treating the inorganic powder and the polyvinyl alcohol resin, the ratio of the amount of carbon remaining after firing to the amount of carbon added by the polyvinyl alcohol resin, which is an organic compound, is increased. A carbon-containing layer can be formed. As a result, the electron conductivity of the positive electrode material is improved, and lithium ions easily move at the interface between the positive electrode material and the electrolyte, so that a positive electrode material having an excellent discharge capacity can be obtained.

  In addition, when a polyvinyl alcohol-based resin is used, the ratio of the amount of carbon remaining after firing to the amount of added carbon increases, and the details of why the carbon-containing layer can be uniformly formed on the surface of the inorganic powder are unknown. However, it is presumed that the hydrophilic group of the polyvinyl alcohol resin is electrically attracted to the hydroxyl groups existing over the entire surface of the inorganic powder, and the molecules of the polyvinyl alcohol resin are easily adsorbed uniformly on the surface of the inorganic powder. Is done.

The inorganic powder has a mol% composition of Li ₂ O + Na ₂ O 10-50%, MnO ₂ + CoO + NiO + Fe ₂ O ₃ 20-65% and SiO ₂ + P ₂ O ₅ + Al ₂ O ₃ + B ₂ O ₃ 10-50%. It is preferable to contain. The reason for limiting the composition in this way will be described below.

Li ₂ O + Na ₂ O is a main component of crystals made of a polyanion compound. The content of Li ₂ O + Na ₂ O is preferably 10 to 50%, more preferably 15 to 45%, and still more preferably 20 to 40%. When the content of Li ₂ O is too small or too large, crystals made of a polyanion compound are difficult to precipitate.

MnO ₂ , CoO, NiO, and Fe ₂ O ₃ are all the main components of crystals made of a polyanion compound. These components may be contained independently and may contain 2 or more types. These components are preferably 20 to 65% in total, more preferably 25 to 60%, and even more preferably 30 to 55%. If the total amount of these components is too small, crystals consisting of a polyanion compound are difficult to precipitate. On the other hand, when the total amount of these components is too large, it becomes difficult to precipitate crystals composed of a polyanion compound, and unwanted heterogeneous crystals are likely to precipitate.

SiO ₂ + P ₂ O ₅ + Al ₂ O ₃ + B ₂ O ₃ is also a main component of a crystal made of a polyanion compound, forms a hydroxyl group on the surface of the inorganic powder, and uniformly adsorbs the molecules of the polyvinyl alcohol resin on the surface. It is a component that makes it easier. The content of SiO ₂ + P ₂ O ₅ + Al ₂ O ₃ + B ₂ O ₃ is preferably 10 to 50%, more preferably 15 to 45%, and still more preferably 20 to 40%. When the content of SiO ₂ + P ₂ O ₅ + Al ₂ O ₃ + B ₂ O ₃ is too small or too large, crystals made of a polyanion compound are difficult to precipitate.

In addition to the above components, for example, Nb ₂ O ₅ , TiO ₂ , V ₂ O ₅ , Cr ₂ O ₃ , SiO ₂ , B ₂ O ₃ , GeO ₂ , Al ₂ O ₃ , Ga ₂ O ₃ , Sb ₂ O ₃ Alternatively, Bi ₂ O ₃ may be added. Among these components, Nb ₂ O ₅ and V ₂ O ₅ are components of crystals composed of a polyanion compound and have an effect of improving glass forming ability. TiO ₂ and Cr ₂ O ₃ are components of crystals made of a polyanion compound. Further, SiO ₂ , B ₂ O ₃ , GeO ₂ , Al ₂ O ₃ , Ga ₂ O ₃ , Sb ₂ O ₃ , and Bi ₂ O ₃ have an effect of improving glass forming ability. These components are the total amount, and are mol% in terms of oxide, preferably 0.1 to 25%, more preferably 0.3 to 20%. If the total amount of the above components is too small, the above effect is difficult to obtain, and if it is too large, the amount of crystals deposited from the polyanion compound tends to decrease.

Among these, Nb ₂ O ₅ is an effective component for obtaining a homogeneous positive electrode active material or for easily forming an amorphous phase, as well as being a crystal component composed of a polyanion compound. The content of Nb ₂ O ₅ is preferably 0.1 to 20%, more preferably 0.2 to 10%, and particularly preferably 0.3 to 5%. If the content of Nb ₂ O ₅ is too small, it is difficult to obtain the above effect. On the other hand, when the content of Nb ₂ O ₅ is too large, heterogeneous crystals are precipitated during crystallisation, the charge-discharge characteristics of the battery tends to decrease.

  Inorganic powder is obtained by compounding raw material powder and using the obtained raw material powder by chemical vapor phase synthesis process such as melting process, sol-gel process, spraying solution mist into flame, mechanochemical process, etc. .

  Specifically, the inorganic powder is produced by a method including (0-a) a step of melting a raw material powder to vitrify, and (0-b) a step of forming the molten glass and then pulverizing it. According to this method, a homogeneous inorganic powder containing Li, P and O can be produced at a low cost.

  In the step (0-a), the melting temperature may be appropriately adjusted so that the raw material powder is uniformly melted. Specifically, it is preferably 900 ° C. or higher, particularly 1000 ° C. or higher. Although an upper limit is not specifically limited, Since it will lead to an energy loss when too high, it is preferable that it is 1500 degrees C or less, especially 1400 degrees C or less.

  In the step (0-b), the method for forming the molten glass is not particularly limited. For example, the molten glass may be poured between a pair of cooling rolls and formed into a film shape while rapidly cooling, or the molten glass may be poured out into a mold and formed into an ingot shape.

  Moreover, the grinding | pulverization method of the molded object in a process (0-b) is not specifically limited, General grinding | pulverization apparatuses, such as a ball mill and a bead mill, can be used. In addition, you may perform simultaneously the process of grind | pulverizing a molded object, and the process of mixing subsequent polyvinyl alcohol-type resin. In this way, the number of processes can be reduced and the cost can be reduced.

  The average particle size of the inorganic powder is 1.8 μm or less, preferably 1.6 μm or less, and more preferably 1.4 μm or less. If the average particle size of the inorganic powder is too large, the specific surface area becomes small and lithium ions are difficult to diffuse, and the internal resistance tends to increase. As a result, lithium ion conductivity at the interface between the positive electrode material and the electrolyte tends to decrease, and the discharge capacity tends to decrease. On the other hand, the lower limit is not particularly limited, but if the average particle diameter of the inorganic powder is too small, the cohesive force between the positive electrode material particles becomes strong, and is difficult to disperse when formed into a paste, and easily aggregates and becomes coarse particles. As a result, the internal resistance of the electrode increases and the output voltage tends to decrease. In addition, the specific surface area of the positive electrode material becomes too large, and a large amount of dispersion medium is required to form a paste. As a result, the electrode density tends to decrease and the discharge capacity per unit volume of the electrode tends to decrease. In addition, there is a problem that cracks are likely to occur when the electrode is dried, and further, the metal component of the inorganic powder is eluted in the electrolyte, resulting in a shortened battery life. Therefore, the average particle size of the inorganic powder is preferably 0.05 μm or more, more preferably 0.1 μm or more, and further preferably 0.2 μm or more.

In the present invention, the average particle diameter of the inorganic powder means D ₅₀ (volume-based average particle diameter), which is a value measured by a laser diffraction scattering method.

  Examples of the polyvinyl alcohol resin include unmodified polyvinyl alcohol, diacetone acrylamide modified polyvinyl alcohol, ethylene modified polyvinyl alcohol, acrolein modified polyvinyl alcohol, carboxyl modified polyvinyl alcohol, alkylene oxide modified polyvinyl alcohol, and polyvinyl alcohol / poly (meth). Acrylic acid (and / or its salt) block copolymer, long chain alkyl vinyl ether modified polyvinyl alcohol, etc. are mentioned.

  The saponification degree of the polyvinyl alcohol-based resin is preferably 70 to 99%, more preferably 80 to 90%. If the degree of saponification is too low, the water-solubility of the polyvinyl alcohol-based resin will be low, so when the inorganic powder and the polyvinyl alcohol-based resin are mixed using pure water, the polyvinyl alcohol-based resin is difficult to adsorb on the surface of the inorganic powder. Become. On the other hand, if the degree of saponification is too high, the polyvinyl alcohol-based resin is easily gelled, and it becomes difficult to form a homogeneous aqueous solution, so the polyvinyl alcohol-based resin cannot be uniformly adsorbed on the surface of the inorganic powder, and the carbon-containing layer that is formed The thickness tends to be non-uniform.

  The polymerization degree of the polyvinyl alcohol-based resin is preferably 100 to 1000, and more preferably 300 to 700. If the degree of polymerization is too low, the ratio of the amount of carbon remaining after firing relative to the amount of added carbon decreases, so the electronic conductivity of the positive electrode material tends to decrease and the discharge capacity tends to decrease. If the degree of polymerization is too high, the polymer chain becomes longer and self-aggregation of the polymer occurs to lower the water solubility, so that the thickness of the formed carbon-containing layer tends to be uneven.

  The amount of added carbon contained in the mixture of the inorganic powder and the carbon source is mass%, preferably 0.01 to 50%, more preferably 0.1 to 30%, and more preferably 1 to 20%. More preferably. If the amount of added carbon is too small, the formation of the carbon-containing layer tends to be insufficient. On the other hand, if the amount of added carbon is too large, the thickness of the carbon-containing layer is increased, the movement of lithium ions is hindered, and the discharge capacity tends to decrease.

  The “added carbon amount” represents mass% of carbon contained in the mixture of the carbon source and the inorganic powder, and is obtained by multiplying the mass ratio of carbon atoms contained in the carbon source by the content of the carbon source.

  Next, in the step (2), a carbon-containing layer is formed on the surface of the inorganic powder by heat-treating the mixture of the inorganic powder and the polyvinyl alcohol resin. Thereby, the positive electrode material which consists of inorganic powder by which the surface was coat | covered with the carbon containing layer is obtained. Furthermore, it is more preferable that the step (2) forms a carbon-containing layer on the surface of the inorganic powder and precipitates a crystal containing a polyanion compound because the manufacturing process can be simplified.

Here, the polyanion compound is a complex compound containing at least one alkali metal element and at least one transition metal element, a phosphate, a silicate, a borate, a sulfate, and a combination thereof. Specifically, LiFePO ₄ , LiMnPO ₄ , LiNiPO ₄ , LiCoPO ₄ , NaFePO ₄ , NaMnPO _{4 and} other general formulas RM _x A _1-x PO ₄ (R is at least one selected from Li and Na, M is at least one selected from Mn, Co, Ni, and Fe, A is at least one selected from Nb, Ti, V, and Cr, and an olivine type compound represented by 0 <x ≦ 1), NaFePO maricite type compounds such as _{4, Li 3 Fe 2 (PO} 4) 3, Na 3 Fe 2 (PO 4) _3, etc. NASICON-type _{Things, Li 2 FeP 2 O 7,} Li 2 MnP 2 O 7, Na 2 FeP 2 pyrophosphates _{O 7, etc., Li 2 FeSiO 4, Li 2} MnSiO 4, Li 2 NiSiO 4, Li 2 CoSiO 4 like Kay _salt, LiFeBO _3, LiMnBO _3, borates such _{NaFeBO 3, Li 3 Fe 2 (} SO 4) 3 or the like sulfates, and the like. Among them, the general formula RM _x A _1-x PO ₄ (R is at least one selected from Li and Na, M is at least one selected from Mn, Co, Ni, and Fe, and A is Nb, Ti, V, And an olivine type compound represented by 0 <x ≦ 1) is preferable because it is a positive electrode material having high capacity, excellent cycle characteristics, and high safety.

  The heat treatment temperature is preferably 550 to 900 ° C, and more preferably 600 to 850 ° C. When the heat treatment temperature is too low, crystals made of a polyanion compound are difficult to precipitate. On the other hand, if the heat treatment temperature is too high, heterogeneous crystals are likely to precipitate, and lithium ion conductivity may be reduced.

  What is necessary is just to adjust suitably the heat processing time so that the crystal | crystallization consisting of a polyanion compound fully precipitates, and, specifically, it is preferable that it is 10 to 180 minutes, and it is more preferable that it is 20 to 120 minutes.

  The heat treatment is preferably performed in an inert or reducing atmosphere. Thereby, the polyvinyl alcohol-type resin adsorbed on the inorganic powder surface is reduced, and a carbon-containing layer can be formed on the inorganic powder surface. Furthermore, crystals made of a polyanion compound can be obtained at a high rate.

The specific surface area of the positive electrode material obtained by the production method of the present invention is preferably 5 m ² / g or more, and more preferably 15 m ² / g or more. When the specific surface area of the positive electrode material satisfies the above range, the contact area between the positive electrode material and the electrolyte is increased, the exchange of lithium ions and electrons is facilitated, and the discharge capacity can be improved. On the other hand, the upper limit is not particularly limited, but if it is too large, moisture tends to be adsorbed on the surface of the positive electrode material, which may cause ignition during charging and discharging. Therefore, the specific surface area of the positive electrode material is preferably 100 m ² / g or less, more preferably 80 m ² / g or less, and further preferably 60 m ² / g or less.

  In the positive electrode material obtained by the production method of the present invention, the carbon content is mass%, preferably 0.01 to 20%, more preferably 0.1 to 10%, more preferably 0.5 to More preferably, it is 5%. When there is too little carbon content, formation of a carbon content layer tends to become insufficient. On the other hand, when the carbon content is too large, the content of crystals made of a polyanion compound is relatively small, and the discharge capacity per unit mass of the positive electrode material tends to be small.

The positive electrode material for an electricity storage device of the present invention preferably has a ratio of the peak intensity D of 1300～1400Cm ^-1 to the peak intensity G of 1550～1650Cm ^-1 in Raman spectroscopy (D / G) is less than or equal to 1, 0 More preferably, it is 8 or less. Furthermore, when the inorganic powder contains P, the ratio (F / G) of the peak intensity F derived from the phosphate component of the polyanion compound to the peak intensity G is preferably 0.5 or less, and is 0.1 or less. More preferably.

  Here, the peak intensity G is derived from crystalline carbon, and the peak intensity D is derived from amorphous carbon. Therefore, the smaller the value of the peak intensity ratio D / G, the closer the carbon-containing layer is to crystalline, and the higher the electronic conductivity. Moreover, the peak intensity F is derived from a crystal made of a phosphate of a polyanion compound. Therefore, the smaller the value of the peak intensity ratio F / G, the higher the proportion of the inorganic powder surface covered with the crystalline carbon-containing layer, and the higher the electron conductivity, the better the discharge capacity. A positive electrode material is obtained.

  The carbon-containing layer is preferably a porous structure having a large number of pores because the specific surface area tends to increase.

  In the inorganic powder, the content of the crystal composed of the polyanion compound is preferably 20% or more by mass%, more preferably 50% or more, and further preferably 70% or more. When the content of the crystal composed of the polyanion compound is too small, the discharge capacity tends to decrease. In addition, although it does not specifically limit about an upper limit, Actually it is preferable that it is 99% or less, and it is more preferable that it is 95% or less.

  As the crystallite size of the crystal made of the polyanion compound is smaller, the particle diameter of the positive electrode material powder can be reduced, and the electron conductivity can be improved. Specifically, the crystallite size is preferably 100 nm or less, and more preferably 80 nm or less. The lower limit is not particularly limited, but is actually 1 nm or more, and further 10 nm or more. The crystallite size is determined according to Scherrer's formula from the analysis result of powder X-ray diffraction.

  The positive electrode material for an electricity storage device of the present invention preferably has a tap density of 0.3 g / ml or more, and more preferably 0.5 g / ml or more. If the tap density is too small, the electrode density decreases and the discharge capacity per unit volume of the battery tends to decrease. The upper limit is approximately a value corresponding to the true specific gravity. However, considering the agglomeration of the powder, the upper limit is practically 5 g / ml or less, and further 4 g / ml or less. In the present invention, the tap density is a value measured under tapping conditions of tapping stroke: 10 mm, tapping frequency: 250 times, tapping speed: 2 times / 1 second.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to these Examples.

Example 1
(1) Preparation of inorganic powder Using lithium metaphosphate (LiPO ₃ ), lithium carbonate (Li ₂ CO ₃ ), ferric oxide (Fe ₂ O ₃ ) and niobium oxide (Nb ₂ O ₅ ) as raw materials, in mol% , Li ₂ O 35.1%, Fe ₂ O ₃ 32.2%, P ₂ O ₅ 32.2%, Nb ₂ O ₅ 0.5% composition of raw material powder, For 1 hour in the atmosphere. Thereafter, molten glass was poured into a pair of rolls and formed into a film shape while rapidly cooling to produce crystalline glass.

The obtained crystalline glass was crystallized by heat treatment at 800 ° C. for 30 minutes, followed by ball milling using Al ₂ O ₃ cobblestone of φ20 mm for 5 hours, and then in ethanol using φ5 mm ZrO ₂ boulder. Was milled for 40 hours, and bead milling in ethanol using ZrO ₂ beads having a diameter of 0.3 mm for 8 hours to obtain crystallized glass powder (inorganic powder) having an average particle size of 0.4 μm.

(2) Production of positive electrode material for electricity storage device 90.1% of inorganic powder obtained in mass%, unmodified polyvinyl alcohol as carbon source (polymerization degree: 500 degree of saponification: 87.18) 9.9% ( The amount of added carbon (4.7%) was thoroughly mixed with pure water and then dried at 100 ° C. for about 1 hour. Thereafter, a heat treatment was performed at 800 ° C. for 30 minutes to obtain a positive electrode material in which a carbon-containing layer was formed on the surface of the inorganic powder. When the obtained positive electrode material was confirmed by a powder X-ray diffraction pattern, the diffraction line from the olivine-type LiFePO ₄ has been confirmed.

(3) Evaluation of positive electrode material for electricity storage device The amount of carbon contained in the obtained positive electrode material and the discharge capacity at 0.1 C and 1 C rates were measured by the following methods. The results are shown in Table 1.

  The carbon content was measured using a simultaneous carbon / sulfur quantitative analyzer (model number: EMIA-920V, method: high frequency induction heating furnace-infrared absorption method) manufactured by Horiba.

  The discharge capacity was evaluated as follows.

With respect to the positive electrode material, polyvinylidene fluoride as a binder and ketjen black as a conductive substance were weighed so as to be positive electrode material: binder: conductive substance = 80: 10: 10 (mass ratio). After being dispersed in methyl pyrrolidone, it was sufficiently agitated with a rotation / revolution mixer to form a slurry. Next, using a doctor blade with a gap of 150 μm, the obtained slurry was coated on a 20 μm thick aluminum foil as a positive electrode current collector, dried at 70 ° C. in a dryer, and then between a pair of rotating rollers The electrode sheet was obtained by pressing at 1 t / cm ² . The electrode sheet was punched to a diameter of 11 mm with an electrode punching machine and dried at 170 ° C. for 10 hours to obtain a circular working electrode.

Next, the obtained working electrode was placed on the lower lid of the coin cell with the aluminum foil surface facing down, and then dried on a vacuum at 60 ° C. for 8 hours under a reduced pressure of 16 mm in polypropylene porous membrane (Hoechst Celanese) A test battery was manufactured by laminating a separator made of Celgard # 2400) and metallic lithium as a counter electrode. As the electrolytic solution, 1M LiPF ₆ solution / EC: DEC = 1: 1 (EC = ethylene carbonate DEC = diethyl carbonate) was used. The test battery was assembled in an environment with a dew point temperature of −40 ° C. or lower.

  A charge / discharge test was performed using a test battery, and the discharge capacities at 0.1 C and 1 C rates were measured. The charge / discharge test was performed as follows. Charging (release of lithium ions from the positive electrode material) was performed by CC (constant current) charging from 2V to 4.2V. The discharge (occlusion of lithium ions into the positive electrode material) was performed by discharging from 4.2V to 2V.

Moreover, the peak intensity ratios D / G and F / G in the Raman spectrum were measured. For Raman spectroscopy measurement, RAMASCOPE made by Renishaw, which is a Raman spectrometer, was used. The resulting chart subjected to baseline correction for the calculated peak intensity F of 900~1000cm ^-1, D peak intensity of 1300～1400Cm ^-1, the peak intensity of 1550～1650Cm ^-1 as G, and the peak intensity The peak intensity ratios D / G and F / G were obtained.

(Comparative Example 1)
By mass%, 87.8% of the inorganic powder obtained in Example 1 and 12.2% of citric acid as a carbon source (4.6% as the amount of added carbon) were sufficiently mixed using pure water. Other than that, a positive electrode material was produced in the same manner as in Example 1. When the obtained positive electrode material was confirmed by a powder X-ray diffraction pattern, the diffraction line from the olivine-type LiFePO ₄ has been confirmed.

  The carbon content of the obtained positive electrode material and the discharge capacity at 0.1 C and 1 C rates were measured in the same manner as in Example 1. The peak intensity ratios D / G and F / G in the Raman spectrum were measured in the same manner as in Example 1. The results are shown in Table 1.

  As is apparent from Table 1, the discharge capacity of Example 1 was higher than that of Comparative Example 1. In Example 1, the ratio of the carbon content to the added carbon content of the carbon source (carbon residual ratio) was higher than that in Comparative Example 1. In Example 1, the peak intensity ratio F / G in the Raman spectrum was smaller than that in Comparative Example 1, and the ratio of the inorganic powder surface covered with the carbon-containing layer was high.

(Example 2)
Lithium metaphosphate (LiPO ₃ ), lithium carbonate (Li ₂ CO ₃ ), ferric oxide (Fe ₂ O ₃ ) and manganese dioxide (MnO ₂ ) are used as raw materials, and in mol%, Li ₂ O 33.3%, A positive electrode material was produced in the same manner as in Example 1 except that the raw material powder was prepared to have a composition of Fe ₂ O ₃ 6.7%, P ₂ O ₅ 33.3%, and MnO ₂ 26.7%. did. When the obtained positive electrode material was confirmed by a powder X-ray diffraction pattern, the diffraction line from olivine _LiMn 0.8 _Fe 0.2 PO ₄ was confirmed.

  The carbon content of the obtained positive electrode material and the discharge capacity at 0.1 C and 1 C rates were measured in the same manner as in Example 1. The results are shown in Table 2.

(Comparative Example 2)
78.2% of the inorganic powder obtained in Example 2 in mass%, polyoxyethylene nonylphenyl ether as a carbon source (HLB value: 13.3 weight average molecular weight: 660) 21.8% (as added carbon amount, 13.8%) was thoroughly mixed with pure water. Other than that, a positive electrode material was produced in the same manner as in Example 1. When the obtained positive electrode material was confirmed by a powder X-ray diffraction pattern, the diffraction line from olivine _LiMn 0.8 _Fe 0.2 PO ₄ was confirmed.

  The carbon content of the obtained positive electrode material and the discharge capacity at 0.1 C and 1 C rates were measured in the same manner as in Example 1. The results are shown in Table 2.

  In Example 2, as compared with Comparative Example 2, the ratio of carbon content to the added carbon amount of the carbon source (carbon residual ratio) was high, and the discharge capacity was high.

  The positive electrode material for an electricity storage device produced by the production method of the present invention is suitable for portable electronic devices such as notebook computers and mobile phones, electric vehicles, and the like.

Claims (6)

(1) An inorganic powder comprising a polyanionic positive electrode material containing at least one element selected from Li and Na, at least one element selected from Si, P, Al and B, and O, and a saponification degree of 70 A step of mixing a polyvinyl alcohol-based resin having a degree of polymerization of 100 to 1000% to obtain a mixture;
(2) forming a carbon-containing layer on the surface of the inorganic powder by heat-treating the mixture;
The manufacturing method of the positive electrode material for electrical storage devices characterized by including.   The method for producing a positive electrode material for an electricity storage device according to claim 1, wherein the step (2) forms a carbon-containing layer on the surface of the inorganic powder and precipitates a crystal containing a polyanion compound. The inorganic powder is expressed in mol% in terms of oxide, Li ₂ O + Na ₂ O 10-50%, MnO ₂ + CoO + NiO + Fe ₂ O ₃ 20-65% and SiO ₂ + P ₂ O ₅ + Al ₂ O ₃ + B ₂ O ₃ 10 The method for producing a positive electrode material for an electricity storage device according to claim 1 or 2, comprising 50%.   The inorganic powder is produced by a method including (0-a) a step of melting and vitrifying the raw material powder, and (0-b) a step of pulverizing the molten glass after molding. The manufacturing method of the positive electrode material for electrical storage devices in any one of Claims 1-3.   The method for producing a positive electrode material for an electricity storage device according to any one of claims 1 to 4, wherein the inorganic powder is a crystalline glass powder or a crystallized glass powder.   The method for producing a positive electrode material for an electricity storage device according to any one of claims 1 to 5, wherein the inorganic powder has an average particle size of 1.8 µm or less.