JP4761239B2 - Non-aqueous secondary battery electrode material, method for producing the same, and non-aqueous secondary battery using the same - Google Patents

Description

  The present invention relates to an electrode material for a non-aqueous secondary battery, a method for producing the same, and a non-aqueous secondary battery using the same.

Since non-aqueous secondary batteries have a high capacity, there are great expectations for their development. Conventionally, as a negative electrode active material of a non-aqueous secondary battery, a natural or artificial graphite-based carbon material (carbon-based negative electrode material) capable of inserting and removing Li ions has been used. Along with the spread of miniaturized and multifunctional mobile phones, more non-aqueous secondary batteries, such as low crystalline carbon, Si (silicon), Sn (tin), etc. A material capable of containing Li is attracting attention as a negative electrode material. For example, a non-aqueous secondary battery using the _{Li t Si (0 ≦ t ≦} 5) as an anode active material has been disclosed (e.g., see Patent Document 1).

Batteries used in advanced equipment such as mobile phones are required to have high cycle performance and high heavy load characteristics as well as high capacity. However, since the negative electrode active material containing Si or the like has a large expansion / contraction caused by insertion / extraction of Li, it cannot be said that the cycle performance is good. Furthermore, since the speed of the alloying reaction with Li is not large, it is difficult to obtain good heavy load characteristics. Therefore, as negative electrode materials excellent in cycle characteristics and heavy load characteristics, oxides containing elements such as Ti, Zr, V, Nb, Cr, Mo, W, and lithium-titanium oxides having a spinel structure (Li ₄ Ti ₅ O ₁₂₎ or the like has been disclosed (e.g., Patent Document 2, non-Patent Document 1).
JP 7-29602 A Japanese Patent Laid-Open No. 7-302587 T. Ohzuku, A. Ueda, N. Yamamoto “Journal of the Electrochemical Society 1995, vol. 142, p. 1431

  However, since the above oxide has lower electrical conductivity than the carbon-based negative electrode material, the electric resistance is large. Therefore, the secondary battery using the above oxide has a problem that a large amount of conductive assistant is required for forming the electrode, and as a result, the discharge capacity becomes small.

The electrode material of another nonaqueous secondary battery of the present invention includes a plurality of oxide particles containing at least one element selected from the group consisting of Ti, Zr, V, Nb, Cr, Mo, and W. A secondary layer and a coating layer that covers the secondary particle and includes a conductive carbon material are included, and the coating layer is included in a ratio of 5 wt% or less with respect to the total weight.

The electrode material of another non-aqueous secondary battery of the present invention includes a plurality of oxide particles containing at least one element selected from the group consisting of Ti, Zr, V, Nb, Cr, Mo, and W. A composite particle including a conductive material, the composite particle including the conductive material therein, and a coating layer that covers the composite particle and includes a conductive carbon material, and the coating layer Is contained at a ratio of 5 wt% or less with respect to the total weight.

The method for producing an electrode material for a non-aqueous secondary battery according to the present invention includes: (a) oxide particles containing at least one element selected from the group consisting of Ti, Zr, V, Nb, Cr, Mo, and W Spraying and drying a dispersion liquid dispersed in a dispersion medium to produce secondary particles containing a plurality of the particles, and (b) heating the secondary particles and the hydrocarbon-based gas, And a step of coating the secondary particles with a carbon material generated by thermal decomposition of a hydrocarbon-based gas.

Another method for producing the electrode material of the nonaqueous secondary battery of the present invention is as follows: (a) an oxide containing at least one element selected from the group consisting of Ti, Zr, V, Nb, Cr, Mo, and W Spraying and drying a dispersion liquid in which the particles and the conductive material are dispersed in a dispersion medium, the composite particles including a plurality of the oxide particles and the conductive material, wherein the conductive material is contained therein a step of fabricating the included the composite particles, coating the (b) the composite particles and then heating the hydrocarbon gas, wherein the composite particle hydrocarbon gas is a carbon material produced by thermal decomposition And a process.

  ADVANTAGE OF THE INVENTION According to this invention, the electrode material of a non-aqueous secondary battery which is excellent in cycling characteristics and heavy load discharge characteristics and can realize a high-capacity non-aqueous secondary battery can be provided.

( Reference form 1)
Below, the manufacturing method of the electrode material of the nonaqueous secondary battery of the reference form 1 is demonstrated.

  First, an oxide containing at least one element selected from the group consisting of Ti, Zr, V, Nb, Cr, Mo, and W is prepared. The average particle size of the oxide is usually 0.01 to 2 μm, particularly 0.1 to 1 μm.

  The oxide having an average particle size of 2 μm or less can be obtained by pulverizing the oxide by a wet method or a dry method. Especially, it is preferable to grind | pulverize wet. In dry pulverization with a dry jet mill or the like, it is difficult to pulverize the oxide with good uniformity, and the pulverized particles also reaggregate. And re-aggregation of the pulverized particles can be suppressed. Examples of the solvent used for wet pulverization include water and alcohols such as ethanol.

The oxide may be any of crystalline, amorphous, or amorphous. In particular, Ti, V, Nb, Mo, and W having 0 or 5 d electrons are preferably included. Specifically, for _{example, Li 4 Ti 5 O 12,} TiO 2, V 2 O 5, WO 3, is preferably MoO _3, or Nb ₂ O _5. These oxides are not easily decomposed by heat in the step of heating the oxide particles and the hydrocarbon-based gas in the gas phase, which will be described later.

Next, the oxide particles and the hydrocarbon-based gas are heated in a gas phase, and a carbon material generated by thermal decomposition of the hydrocarbon-based gas is deposited on the surface of the particles. Thus, according to the vapor deposition (CVD) method, the hydrocarbon-based gas spreads to every corner of the oxide particles, and a thin and uniform coating (coating layer) containing a carbon material on the surface of the oxide particles. ) Can be formed. Thus, according to the manufacturing method of an electrode material of the nonaqueous secondary battery of the present reference embodiment, the surface of the oxide particles, can impart good uniformity conductivity with a small amount of the carbon material.

  Regarding the weight ratio of the coating layer to the total weight of the electrode material and the conductivity of the carbon material contained in the coating layer, the processing time of the vapor deposition (CVD) method and the thermal decomposition temperature of hydrocarbon gas (processing temperature) It can be controlled by changing etc. The treatment time varies depending on the surface area of the oxide particles, but is usually about 10 to 180 minutes. The treatment temperature varies depending on the type of hydrocarbon gas, but is usually 600 ° C to 1000 ° C.

  As the liquid source of the hydrocarbon-based gas, liquid hydrogen such as toluene, benzene, xylene, mesitylene and the like can be used. In particular, toluene that is easy to handle is preferable. A hydrocarbon-based gas can be obtained by vaporizing these.

  Next, the electrode material of the non-aqueous secondary battery produced by the above manufacturing method will be described.

Electrode material of the nonaqueous secondary battery of the present reference embodiment, Ti, Zr, V, Nb , Cr, Mo, and the particles of oxide containing at least one element selected from the group consisting of W, of the particles And a coating layer containing a pyrolytic component (carbon material having conductivity) of a hydrocarbon gas. The electrode material includes a coating layer at a ratio of 5 wt% or less with respect to the total weight of the electrode material. In addition, 0.01 wt% or more is suitable for the lower limit of the weight ratio with respect to the total weight of the electrode material of the coating layer. Coating layer comprising a carbon material having conductivity, if it contains more than 0.01 wt% relative to the total weight of the electrode material, the electrode material of the nonaqueous secondary battery of the present reference embodiment, sufficient as an electrode material Conductivity can be provided.

Ti which constitutes the electrode material of this preferred embodiment, Zr, V, Nb, Cr, Mo, and oxides containing at least one element selected from the group consisting of W, since the volume change associated with insertion of Li is small Excellent cycle characteristics. Moreover, since insertion and removal of Li are performed smoothly and the conductivity of Li is very high, the heavy load characteristics are also excellent. The oxide surface is covered with a coating layer containing a conductive carbon material and having a weight ratio of only 0.01 wt% to 5 wt% with respect to the total weight of the electrode material. Conductivity is imparted with good uniformity. Therefore, when the electrode material of the present reference embodiment for the formation of electrodes, it is possible to use a sufficient amount of the electrode material by subtracting the amount of conductive additive. Thus, according to the electrode material of this preferred embodiment, excellent cycle characteristics and heavy load discharge characteristics, and it is possible to realize a high capacity non-aqueous secondary battery.

The smaller the average particle diameter of the oxide particles, the larger the reaction area with Li, which is preferable. However, it is usually 0.01 to 2 μm, and particularly preferably 0.1 to 1 μm. The oxide is preferably Li ₄ Ti ₅ O ₁₂ , TiO ₂ , V ₂ O ₅ , WO ₃ , MoO ₃ , or Nb ₂ O ₅ , for example.

For non-aqueous secondary battery electrode material of this preferred embodiment, the peak intensity existing in the frequency region of 1550 cm ^-1 1650 cm ^-1 on the Raman spectrum is measured using an argon laser with a wavelength of 514.5 nm I ₁ and then, when a peak intensity existing in the frequency region of 1300cm ^-1 ~1400cm ^-1 was I _2, the ratio of I ₂ and _{I 1 (I 2 / I 1} ) is 0.4 to 1. The measurement result by this Raman spectroscopy has shown the characteristic of the surface of an electrode material, ie, the carbon material which comprises a coating layer. The larger the ratio (I ₂ / I ₁ ), the lower the crystallinity.

Next, an example of a non-aqueous secondary battery using the electrode material of the present reference embodiment.

The nonaqueous secondary battery of the present reference embodiment, except for using the electrode material of this preferred embodiment has the similar structure as the common non-aqueous secondary battery conventionally known, also the shape and the like There is no limit. For example, the non-aqueous secondary battery shown in FIG. 1 is a coin-type secondary battery, and the negative electrode 1, the separator 3, the positive electrode 2, and the electrolytic solution are contained in the storage container 4, the gasket 6, and the sealing plate 5. And is contained in a sealed space formed by

The nonaqueous secondary battery of the present reference embodiment, the electrode material of this preferred embodiment is used as a material for the negative electrode. The negative electrode is the electrode material of this preferred embodiment, the mixture comprising the binder (binder) such as a negative electrode mixture paste was obtained by thoroughly kneaded to a suitable solvent, it is applied to the current collector, The negative electrode mixture paste can be formed by controlling to a predetermined thickness and a predetermined electrode density.

  As the binder, starch, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, diacetyl cellulose, polyvinyl chloride, polyvinyl pyrrolidone, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, ethylene-propylene-dienter Polymers (EPDM), sulfonated EPDM, styrene butadiene rubber, butadiene rubber, polybutadiene, fluoro rubber, polyethylene oxide and other polysaccharides, thermosetting resins, thermoplastic resins, other polymers having rubbery elasticity, etc. At least one or two or more of the modified products can be used.

  The positive electrode 2 was prepared by applying a positive electrode mixture paste obtained by adding a suitable solvent to a mixture containing a positive electrode active material, a conductive additive, and a binder and sufficiently kneading the mixture onto a current collector. It can be formed by controlling to a predetermined electrode density.

There are no particular limitations on the positive electrode active material, and various materials can be used. In particular, Li _x CoO ₂ , Li _x NiO ₂ , Li _x MnO ₂ , Li _x Co _y Ni _1-y O ₂ , Li _x Co _y M _{1 -y} O _Z , Li _x Ni _{1 -y My} O _Z , Li _x Mn ₂ O ₄ , Li _x Mn _{2 -y My} O ₄ (M is Mg, Mn, Fe, Co, Ni, Cu At least one selected from the group consisting of Zn, Al, and Cr, such as 0 ≦ x ≦ 1.1, 0 <y <1.0, 2.0 ≦ z ≦ 2.2). Is preferred. As the binder, the same binder as that used for forming the negative electrode 1 can be used.

  The separator 3 is preferably one having sufficient strength and capable of holding a large amount of electrolyte. From such a viewpoint, polyethylene, polypropylene, or ethylene-propylene copolymer having a thickness of 10 to 50 μm and an aperture ratio of 30 to 70% is preferable. A microporous film or a nonwoven fabric containing a polymer is preferred.

  As the electrolytic solution, one prepared by dissolving the following inorganic ion salt in the following solvent can be used.

  Examples of the solvent include propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate (MEC), γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivative, sulfolane, 3-methyl- Aprotic organic solvents such as 2-oxazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, diethyl ether, 1,3-propane sultone One, or a mixture solvent obtained by mixing two or more can be used.

As the inorganic ion salt, Li salt, for _{example, LiClO 4, LiBF 4, LiPF} 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, LiB 10 Cl 10, lower aliphatic carboxylic acids Li, LiAlCl ₄ , LiCl, LiBr, LiI, chloroborane Li, Li tetraphenylborate, or the like can be used alone or in combination.

Among the electrolytic solutions in which the inorganic ion salt is dissolved in the solvent, among them, at least one selected from the group consisting of 1,2-dimethoxyethane, diethyl carbonate and methyl ethyl carbonate, ethylene carbonate or propylene carbonate, An electrolyte solution in which at least one inorganic ion salt selected from LiClO ₄ , LiBF ₄ , LiPF ₆ , and LiCF ₃ SO ₃ is dissolved in a solvent containing s is preferable. The concentration of the inorganic ion salt in the electrolytic solution is suitably 0.2 to 3.0 mol / dm ³ .

Incidentally, the example shown in FIG. 1 is a nonaqueous secondary battery of the coin-type non-aqueous secondary battery of the present reference embodiment is not particularly limited for its shape, for example, button type, sheet type, square It may be a mold or the like.

In the non-aqueous secondary battery of the present reference embodiment described with reference to FIG. 1, the electrode material of the present reference embodiment, is used as the material of the negative electrode can also be used as a material for the positive electrode. When using the electrode material of this preferred embodiment the positive electrode, the negative electrode active material, for example, a mixture of Li and carbon, or a LiAl, the electrolyte solution, for example, ethylene carbonate (EC) and methylethyl carbonate (MEC And a solution of LiPF ₆ dissolved in a mixed solvent.

(Embodiment 1 )
Below, the manufacturing method of the electrode material of the nonaqueous secondary battery of Embodiment 1 is demonstrated.

First, after preparing a dispersion in which an oxide containing at least one element selected from the group consisting of Ti, Zr, V, Nb, Cr, Mo, and W is dispersed in a dispersion medium, and spraying the dispersion And dried to produce secondary particles containing a plurality of the particles. For example, ethanol or the like is used as the dispersion medium. The average particle size of the secondary particles is usually 0.1 to 20 μm. It is appropriate to spray the dispersion in an atmosphere of 50 to 300 ° C.

  In this step, a dispersion liquid in which the oxide particles and the conductive material are dispersed in a dispersion medium is prepared, sprayed, and then dried to produce composite particles containing the conductive material inside. May be. By adding a conductive material to the dispersion to produce composite particles containing the conductive material inside, an electrode material with a better conductive network can be produced.

Examples of the conductive material include a fibrous or coiled carbon material, a fibrous or coiled metal, and a carbon black having a high specific surface area (50 m ² / g or more) that can easily form a conductive network with oxide particles. It is preferable to use at least one selected from the group consisting of chain black and acetylene black), graphite (artificial graphite, natural graphite), graphitizable carbon and non-graphitizable carbon. As the fibrous or coiled carbon material, PAN-based carbon fiber, pitch-based carbon fiber, vapor-grown carbon fiber, or the like can be used.

The average particle size of the oxide particles constituting the composite particles or the secondary particles is preferably 0.01 to 2 μm, particularly 0.1 to 1 μm. as a method for obtaining, in the same manner as in reference embodiment 1, a method of pulverizing the oxide by a wet it is preferable. When producing composite particles containing a conductive material inside , if the oxide and the conductive material are pulverized by a wet process, the oxide and the conductive material can be mixed uniformly, and a good conductive network is formed inside. The constructed composite particles can be produced. Examples of the solvent used for wet pulverization include water and alcohols such as ethanol.

Next, the composite particles or secondary particles and the hydrocarbon-based gas are heated in the gas phase, and the carbon material generated by the thermal decomposition of the hydrocarbon-based gas is placed on the surface of the composite particles or the secondary particles. Deposit. As described above, according to the vapor deposition (CVD) method, the hydrocarbon-based gas spreads to every corner of the oxide, and on the surface of the composite particle or the secondary particle , the conductive carbon material is contained and thinned. A uniform film (coating layer) can be formed, and a small amount of carbon material can impart conductivity to the oxide with good uniformity. Furthermore, hydrocarbon gas since also diffuses into the interior of the composite particles or secondary particles, can impart conductivity to the composite particles or the secondary particles.

In the manufacturing method of the electrode material of the present embodiment, the treatment temperature (atmosphere temperature) of the vapor phase growth (CVD) method is suitably 600 ° C. to 1000 ° C. as in the case of the reference embodiment 1, and is hydrocarbon. The liquid source of the system gas may be the same as that in Reference Embodiment 1. The treatment time varies depending on the surface area of the composite particles or secondary particles , but is usually about 10 minutes to 180 minutes.

  Next, the electrode material of the non-aqueous secondary battery produced by the manufacturing method described above will be described.

Second electrode material of the nonaqueous secondary battery of the present embodiment, which includes a plurality Ti, Zr, V, Nb, Cr, Mo, that and the particles of oxide containing at least one element selected from the group consisting of W Secondary particles, and a coating layer that covers the surface of the secondary particles and includes a pyrolysis component (carbon material) of a hydrocarbon-based gas. The electrode material includes a coating layer at a ratio of 5 wt% or less with respect to the total weight of the electrode material. In addition, 0.01 wt% or more is suitable for the lower limit of the weight ratio with respect to the total weight of the electrode material of the coating layer. If the coating layer containing a conductive carbon material is included in an amount of 0.01 wt% or more with respect to the total weight of the electrode material, the electrode material of the nonaqueous secondary battery of this embodiment is sufficient as the electrode material It can be provided with a good conductivity.

An oxide containing at least one element selected from the group consisting of Ti, Zr, V, Nb, Cr, Mo, and W constituting the electrode material of this embodiment has a small volume change due to insertion of Li. Therefore, it has excellent cycle characteristics. Moreover, since insertion and removal of Li are performed smoothly and the conductivity of Li is very high, the heavy load characteristics are also excellent. The surface of the secondary particles containing a plurality of such oxide particles is covered with a coating layer containing a conductive carbon material and having a weight ratio of only 0.01 wt% to 5 wt% with respect to the total weight of the electrode material. Therefore, conductivity is imparted to the oxide with good uniformity. Therefore, if the electrode material of the present embodiment is used for forming the electrode, it is possible to use a sufficient amount of the electrode material by reducing the amount of the conductive additive added. Thus, according to the electrode material of the present embodiment, it is possible to realize a non-aqueous secondary battery that is excellent in cycle characteristics and heavy load discharge characteristics and has a high capacity.

The electrode material of the nonaqueous secondary battery of the present embodiment, the peak intensity existing in the frequency region of 1550 cm ^-1 1650 cm ^-1 on the Raman spectrum is measured using an argon laser with a wavelength of 514.5 nm I _When the peak intensity existing in the frequency range of 1300 cm ^{−1 to} 1400 cm ⁻¹ is I ₂ , the ratio of I ₂ to I ₁ (I ₂ / I ₁ ) is 0.4 to ₁ . The measurement result by this Raman spectroscopy has shown the characteristic of the surface of an electrode material, ie, the carbon material which comprises a coating layer. The larger the ratio (I ₂ / I ₁ ), the lower the crystallinity.

In the electrode material of the present embodiment, a conductive material of a type different from the carbon material included in the coating layer may be included in the composite particles. If a conductive material in the interior of including composite particles, can form a better conductive network, the nonaqueous secondary battery produced by using the electrode material of the present embodiment, further the battery characteristics such as cycle characteristics Can be improved.

Examples of the conductive material include a fibrous or coiled carbon material, a fibrous or coiled metal, and a carbon black having a high specific surface area (50 m ² / g or more) that can easily form a conductive network with oxide particles. It is preferable to use at least one selected from the group consisting of chain black and acetylene black), graphite (artificial graphite, natural graphite), graphitizable carbon and non-graphitizable carbon. As the fibrous or coiled carbon material, PAN-based carbon fiber, pitch-based carbon fiber, vapor-grown carbon fiber, or the like can be used.

The electrode material of the non-aqueous secondary battery of the present embodiment produced in this manner can be used as the negative electrode or positive electrode material of the non-aqueous secondary battery, as in Reference Embodiment 1.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

( Reference Example 1)
10 g of Li ₄ Ti ₅ O ₁₂ (BET specific surface area 4 m ² / g, average particle size 0.8 μm) was heated to about 900 ° C. in a boiling bed reactor, and the heated particles consisted of toluene and nitrogen gas 25 A CVD process was performed at about 900 ° C. for 60 minutes by bringing a mixed gas at 0 ° C. into contact therewith. In this way, a carbon material produced by thermal decomposition of the mixed gas was deposited on the particles to form a coating layer, and an electrode material was obtained.

Was subjected to analysis of the surface of the electrode material by Raman spectroscopy, the peak intensity existing in the frequency 1590 cm ^-1 on the Raman spectrum and I _1, when the peak intensity existing in the 1350 cm ^-1 was I _2, the ratio (I ₂ / I ₁ ) was 0.64. An argon laser having a wavelength of 514.5 nm was used as the light source.

When the weight ratio of Li ₄ Ti ₅ O ₁₂ to the coating layer was determined from the weight change before and after the formation of the coating layer, Li ₄ Ti ₅ O ₁₂ (oxide particles): coating layer = 99: 1.

  Next, a coin-type model battery was manufactured using the electrode material. First, a slurry obtained by mixing 90% by weight of the electrode material, 10% by weight of a polyvinylidene fluoride resin (binder), and dehydrated N-methylpyrrolidone is used as a current collector (not shown) made of copper foil. The mixture was applied, dried and rolled to form a mixture layer having a thickness of 50 μm on one surface of the current collector. Thereafter, it was punched to a diameter of 16 mm and dried in a vacuum for 24 hours to obtain a disk-shaped working electrode. The adhesiveness of the mixture layer to the copper foil was good, and the mixture layer was not peeled off from the copper foil even when it was cut or bent. On the other hand, a disk-shaped metal Li (diameter 16 mm, thickness 0.2 mm) was prepared as a counter electrode.

Next, the counter electrode is bonded to a stainless steel storage container, and after placing the separator and the working electrode in this order on the counter electrode, 0.2 ml of electrolyte is injected into the storage container, and a sealing body with a gasket is provided. The inside of the storage container was hermetically sealed to obtain a model battery. As the electrolytic solution, a solution in which LiPF ₆ was dissolved in a solvent in which propylene carbonate and dimethyl carbonate were mixed at a volume ratio of 1: 1 so as to have a concentration of 1 mol / dm ³ was used.

(Example 1 )
Li ₄ Ti ₅ O ₁₂ (BET specific surface area 4 m ² / g, average particle size 0.8 μm) 100 g and polyvinylpyrrolidone (dispersant) 10 g were mixed in ethanol (dispersion medium) 1000 ml, and the resulting mixture was obtained. The slurry was dispersed by a wet jet mill. Using this slurry, secondary particles (average particle size of 3 μm) were prepared by a spray drying method (atmospheric temperature 200 ° C.).

Subsequently, 10 g of secondary particles are heated to about 900 ° C. in a boiling bed reactor, a mixed gas of 25 ° C. composed of toluene and nitrogen gas is brought into contact with the heated secondary particles, and CVD is performed at 900 ° C. for 60 minutes. Processed. In this way, a carbon material generated by thermal decomposition of the mixed gas was deposited on the secondary particles to form a coating layer, and an electrode material was obtained.

When the surface of the electrode material was analyzed by Raman spectroscopy, the peak intensity existing in the frequency region of 1590 cm ⁻¹ on the Raman spectrum was I _1, and the peak intensity existing in the frequency region of 1350 cm ⁻¹ was I When the ratio was ₂ , the ratio (I ₂ / I ₁ ) was 0.62. An argon laser having a wavelength of 514.5 nm was used as the light source.

The weight ratio between Li ₄ Ti ₅ O ₁₂ and the coating layer was determined from the change in weight before and after the formation of the coating layer. The result was Li ₄ Ti ₅ O ₁₂ (oxide particles): coating layer = 98: 2.

Next, a coin-type model battery was fabricated in the same manner as in Reference Example 1 except that the electrode material was used as a working electrode material. The adhesion of the mixture layer to the copper foil was good, and the mixture layer was not peeled off from the copper foil even when it was cut or bent.

(Example 2 )
99 g Li ₄ Ti ₅ O ₁₂ (BET specific surface area 4 m ² / g, average particle size 0.8 μm), 1 g ketjen black (BET specific surface area 800 m ² / g, average particle size 0.05 μm) and polyvinylpyrrolidone (dispersed) Agent) and 10 g of ethanol (dispersion medium) in 1000 ml. The obtained mixture was dispersed in a wet jet mill to form a slurry, and composite particles (average particle size: 3 μm) were prepared by a spray drying method (atmospheric temperature 200 ° C.) using this slurry.

  Subsequently, 10 g of the composite particles are heated to about 900 ° C. in a boiling bed reactor, a mixed gas of 25 ° C. composed of toluene and nitrogen gas is brought into contact with the heated composite particles, and a CVD treatment is performed at 900 ° C. for 60 minutes. went. In this way, a carbon material generated by thermal decomposition of the mixed gas was deposited on the composite particles to form a coating layer, and an electrode material was obtained.

When the surface of the electrode material was analyzed by Raman spectroscopy, the peak intensity existing in the frequency region of 1590 cm ⁻¹ on the Raman spectrum was I _1, and the peak intensity existing in the frequency region of 1350 cm ⁻¹ was I When the ratio was ₂ , the ratio (I ₂ / I ₁ ) was 0.56. An argon laser having a wavelength of 514.5 nm was used as the light source.

Further, when the weight ratio of Li ₄ Ti ₅ O ₁₂ , Ketjen Black and the coating layer was determined from the weight change before and after the formation of the coating layer, Li ₄ Ti ₅ O ₁₂ (oxide particles): Ketjen Black: The coating layer was 98: 1: 1.

Next, a coin-type model battery was produced in the same manner as in Reference Example 1 except that the electrode material was used as a working electrode. The adhesion of the mixture layer to the copper foil was good, and the mixture layer was not peeled off from the copper foil even when it was cut or bent.

(Comparative Example 1)
Li ₄ Ti ₅ O ₁₂ (BET specific surface area 4 m ² / g, average particle size 0.8 μm) and artificial graphite as a conductive assistant were mixed in a mortar to obtain an electrode material. The weight ratio of Li ₄ Ti ₅ O ₁₂ and artificial graphite was 99: 1. Next, in the same manner as in Reference Example 1, a working electrode was produced, and a coin-type model battery was produced. The adhesion of the mixture layer to the copper foil was good, and the mixture layer was not peeled off from the copper foil even when it was cut or bent.

(Comparative Example 2)
Li ₄ Ti ₅ O ₁₂ (BET specific surface area 4 m ² / g, average particle size 0.8 μm) and artificial graphite as a conductive assistant were mixed in a mortar. The weight ratio of Li ₄ Ti ₅ O ₁₂ and artificial graphite was 90:10. Next, in the same manner as in Reference Example 1, a working electrode was produced, and a coin-type model battery was produced. The adhesion of the mixture layer to the copper foil was good, and the mixture layer was not peeled off from the copper foil even when it was cut or bent.

(Comparative Example 3)
Li ₄ Ti ₅ O ₁₂ (BET specific surface area 4 m ² / g, average particle size 0.8 μm) and ketjen black (BET specific surface area 800 m ² / g, average particle size 0.05 μm) as a conductive assistant in a mortar And mixed. The weight ratio of Li ₄ Ti ₅ O ₁₂ and ketjen black was 90:10. Next, in the same manner as in Reference Example 1, a working electrode was produced, and a coin-type model battery was produced. When the working electrode was cut or bent, a part of the mixture layer was peeled off from the copper foil, and the adhesion of the mixture layer to the copper foil was poor.

About the model battery of the reference example 1, Examples 1-2 , and Comparative Examples 1-3, the capacity | capacitance maintenance factor, the discharge capacity, and the heavy load characteristic were investigated with the following method. Moreover, the resistivity of the electrode material produced by the reference example 1, Examples 1-2 , and Comparative Examples 1-3 was calculated | required with the following method. The results are shown in Table 1.

[Capacity maintenance rate]
Reference Example 1, the model batteries of Examples 1-2 and Comparative Examples 1 to 3, in an atmosphere of 25 ° C., after which the battery voltage at a constant current of 0.5mA was charged until 1.0 V, the current value The battery was charged by a constant voltage method until reaching 0.05 mA. Thereafter, the battery was discharged at a constant current of 0.5 mA until the battery voltage became 2.5 V (discharge end voltage), and the discharge capacity was measured. With this as one cycle, the discharge capacity after 100 cycles was measured, and the capacity retention rate after 100 cycles was calculated by the following formula 1.
(Equation 1)
Capacity retention rate (%) = (discharge capacity at the 100th cycle / discharge capacity at the second cycle) × 100

[Discharge capacity]
For the 2nd to 100th cycles, the discharge capacity of the negative electrode was measured for each cycle, and the discharge capacity per unit weight (mAh / g) of the composite layer was calculated from the average value.

[Heavy load discharge characteristics]
For the model batteries of Reference Example 1, Examples 1 and 2 and Comparative Examples 1 to 3, the battery was charged at 0.5 mA / cm ² until the battery voltage reached 1.0 V, and then determined until the current value reached 0.05 mA. The discharge capacity of the second cycle (referred to as “discharge capacity 1”) when charging is performed by the voltage method and discharged to 0.5 V at 0.5 mA / cm ² is obtained. Next, after charging until the battery voltage becomes 1.0 V at 0.5 mA / cm ² , charging is performed by a constant voltage method until the current value becomes 0.05 mA, and the battery voltage becomes 2.5 V at 5 mA / cm ^2. The discharge capacity at the second cycle when the battery is discharged until it is (referred to as “discharge capacity 2”) is obtained. From the measurement results of these discharge capacities, [(discharge capacity 1 / discharge capacity 2) × 100] (%) indicating heavy load characteristics was determined.

[Resistance rate]
While pressing the electrode material at a pressure of 400 kg · f / cm ² with a press machine, the resistivity of the electrode material was measured with a surface resistance meter (Mitsubishi Chemical Corporation, low resistivity meter Loresta-GP, MCP-T600). It was measured.

As shown in Table 1, when the electrode materials of Examples 1 and 2 and the electrode materials of Comparative Examples 2 and 3 are compared, the electrode materials of Examples 1 and 2 are more conductive than the electrode materials of Comparative Examples 2 and 3. Although the weight ratio of the carbon material having a property (coating layer) is much less as 1 wt% to 2 wt% (however, for the electrode material of Example 2 , 1 wt% of the conductive auxiliary (KB ), But the resistivity is orders of magnitude smaller than the electrode materials of Comparative Examples 2 and 3. When comparing the electrode material of Examples 1 and 2 with the electrode material of Comparative Example 1, the electrode material of Examples 1 and 2 includes almost the same amount of coating layer (carbon material) as the electrode material of Comparative Example 1. However, the specific effective value is much smaller than that of the electrode material of Comparative Example 1. As a result, in the electrode materials of Examples 1 and 2 , since the coating layer is formed by the vapor deposition (CVD) method, the hydrocarbon-based gas spreads to every corner of the oxide in the vapor phase. appears to uniformity good conductivity for the oxide is because granted. Therefore, according to the electrode material of the non-aqueous secondary battery of Examples 1 and 2 in which the coating layer is included at a ratio of 5 wt% or less with respect to the total weight, the conductive auxiliary agent is reduced when the electrode is formed. Many electrode materials can be used, and as shown in the results of Table 1, the capacity of the non-aqueous secondary battery can be increased.

The electrode material of Example 2 is in the form of composite particles containing ketjen black as a conductive material therein. For example, the capacity retention rate is higher than that of the electrode material of Reference Example 1, and cycle characteristics, etc. It was confirmed that the battery characteristics of were superior.

Moreover, it has confirmed that the model battery of Examples 1-2 was excellent also about the capacity | capacitance maintenance factor and the heavy load discharge characteristic than the model battery of Comparative Examples 1-3.

When the oxide (Li ₄ Ti ₅ O ₁₂ ) before and after the formation of the coating layer was analyzed by the X-ray diffraction method, no change was found in the X-ray diffraction profile as shown in FIG. From this result, it was confirmed that the oxide (Li ₄ Ti ₅ O ₁₂ ) did not change before and after the formation of the coating layer. Note that CuKα rays were used as the X-ray source, and high-purity silicon was used as the standard material.

  As described above, according to the electrode material of the present invention, it is possible to realize a non-aqueous secondary battery having excellent cycle characteristics and heavy load discharge characteristics and having a high capacity. Therefore, it is suitable as a material for non-aqueous secondary batteries. Yes.

Sectional drawing which shows an example of the non-aqueous secondary battery of this invention X-ray diffraction profile of oxide before and after forming coating layer

DESCRIPTION OF SYMBOLS 1 Negative electrode 2 Positive electrode 3 Separator 4 Storage container 5 Sealing plate 6 Gasket

Claims (10)

Secondary particles containing a plurality of oxide particles containing at least one element selected from the group consisting of Ti, Zr, V, Nb, Cr, Mo, and W;
A coating layer that covers the secondary particles and includes a conductive carbon material;
The electrode material for a non-aqueous secondary battery, wherein the coating layer is included at a ratio of 5 wt% or less with respect to the total weight. A composite particle comprising a plurality of particles of an oxide containing at least one element selected from the group consisting of Ti, Zr, V, Nb, Cr, Mo, and W and a conductive material, The composite particles containing a conductive material;
  A coating layer that covers the composite particles and includes a conductive carbon material;
  The electrode material for a non-aqueous secondary battery, wherein the coating layer is included at a ratio of 5 wt% or less with respect to the total weight.   The conductive material is at least one selected from the group consisting of a fibrous or coiled carbon material, a fibrous or coiled metal, carbon black, graphite, graphitizable carbon, and non-graphitizable carbon. The electrode material of the non-aqueous secondary battery as described in 2.   1550 cm on the Raman spectrum measured using an argon laser with a wavelength of 514.5 nm ^-1 ~ 1650cm ^-1 The peak intensity existing in the frequency region of ₁ 1300cm ^-1 ~ 1400cm ^-1 The peak intensity existing in the frequency region of ₂ The ratio (I ₂ / I ₁ The electrode material for a non-aqueous secondary battery according to any one of claims 1 to 3.   The oxide is Li _Four Ti _Five O ₁₂ TiO ₂ , V ₂ O _Five , WO _Three , MoO _Three Or Nb ₂ O _Five The electrode material for a nonaqueous secondary battery according to any one of claims 1 to 4.   A non-aqueous secondary battery, wherein the electrode material of the non-aqueous secondary battery according to claim 1 is used for a positive electrode or a negative electrode. (A) spraying and drying a dispersion in which oxide particles containing at least one element selected from the group consisting of Ti, Zr, V, Nb, Cr, Mo, and W are dispersed in a dispersion medium; Producing a secondary particle comprising a plurality of said particles;
(B) heating the secondary particles and a hydrocarbon-based gas, and covering the secondary particles with a carbon material generated by thermal decomposition of the hydrocarbon-based gas. A method for producing an electrode material for a non-aqueous secondary battery.   (A) Spraying a dispersion in which oxide particles containing at least one element selected from the group consisting of Ti, Zr, V, Nb, Cr, Mo, and W and a conductive material are dispersed in a dispersion medium And drying to produce a composite particle containing a plurality of the oxide particles and a conductive material, wherein the composite particle contains the conductive material therein;
  (B) heating the composite particles and a hydrocarbon-based gas, and coating the composite particles with a carbon material generated by thermally decomposing the hydrocarbon-based gas. A method for producing an electrode material for a secondary battery.   The oxide is Li _Four Ti _Five O ₁₂ TiO ₂ , V ₂ O _Five , WO _Three , MoO _Three Or Nb ₂ O _Five The method for producing an electrode material for a non-aqueous secondary battery according to claim 7 or 8.   9. The conductive material is at least one selected from the group consisting of a fibrous or coiled carbon material, a fibrous or coiled metal, carbon black, graphite, graphitizable carbon, and non-graphitizable carbon. Or the manufacturing method of the electrode material of the non-aqueous secondary battery of any one of 9 terms.

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