JP2005078985A - Electrode for nonaqueous secondary battery and lithium secondary battery using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode for a nonaqueous secondary battery wherein battery energy density is not reduced, and the impedance in the electrode is not reduced so that a large capacity and excellent cycle characteristics are provided. <P>SOLUTION: A deposition body of ingredient powder consisting of lithium transition metal oxide and inorganic solid electrolyte battery has a positive electrode of which vacancy ratio is under 15%, and conductivity is over 1mS/cm. In a lithium secondary battery formed by interposing iorganic solid electrolyte between a positive electrode active substance and a cathode active substance, the anode active material and/or the cathode active substance are formed with a deposition layer of iorganic solid electrolyte in which metal oxide particles having conductivity are dispersed, and of metal oxide. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a positive electrode for a non-aqueous secondary battery that provides high capacity and excellent cycle characteristics, and a lithium secondary battery using the same.

  Along with the popularization of mobile phones and laptop computers, lithium secondary batteries using insertion and desorption of lithium ions, which can be expected to have high energy density, have attracted attention, and in particular, the demand for space-saving thin rectangular batteries has increased. ing.

  However, in this battery, the electrode containing the active material is composed of an active material, a binder, and a conductive agent, and among these components, the binder and the conductive agent originally do not contribute to the capacity of the electrode. There is a problem that the battery capacity per volume is limited.

  Therefore, as one means for increasing the capacity per unit volume, an attempt has been made to configure the electrode with a sintered body substantially made of an active material. In other words, when the electrode is composed of a sintered body of a component containing an active material, it does not contain a binder, and the conductive agent can be used or reduced in weight. Capacity can be increased. As such a sintered body, a positive electrode made of a sintered body of a lithium transition metal oxide is known (see, for example, Patent Document 1 and Patent Document 2). This sintered body is obtained by press-molding or sheet-molding a lithium transition metal oxide powder or its raw material powder using a mold, and firing the molded body at a predetermined temperature in the presence of oxygen. Yes. However, this sintered body has insufficient conductivity, and performance as a positive electrode is not satisfactory.

  That is, when the sintered body is used as a positive electrode, many pores are usually included in order to allow the electrolyte for ion conduction in the positive electrode to permeate into the sintered body. Therefore, the sintering temperature is extremely low, the lithium transition metal oxide particles constituting the positive electrode are not sufficiently bonded, and the crystal growth of the sintered body at the particle contact portion is insufficient, so that sufficient conductivity cannot be obtained. There was a need for improvement.

  Further, in a conventional lithium secondary battery, a non-aqueous electrolyte or gel polymer dissolved in a non-aqueous solvent is frequently used as an electrolyte. When such a liquid electrolyte is used, there is a problem of leakage of the electrolyte or gel, or smoke generation, and it is necessary to take measures to completely prevent leakage and corrosion outside the battery. In addition, there has been a problem in yield reduction due to the occurrence of an internal short circuit in the electrolyte injection.

In recent years, in order to solve such problems, the development of a solid electrolyte battery with excellent heat resistance and long battery life using an inorganic solid electrolyte such as a metal oxide instead of such a liquid or gel electrolyte has been developed. It is being considered. For example, a battery using a solid electrolyte, in which an electrode active material and a solid electrolyte are mixed for the purpose of reducing battery internal resistance, and a carbon material or a metal is used for conductive particles is known (Patent Literature). 3). However, this battery is not excellent in capacity retention and performance as a solid electrolyte battery is not satisfactory.
As a result of the study, the present inventor has found that this is caused by the reduction of the active material or solid electrolyte during sintering or charging / discharging by graphite contained in the electrode. In other words, in this battery, a part of the elements contained in the crystal structure of the active material or solid electrolyte is reduced, so that the crystal structure and the electrode structure can be easily collapsed, and the capacity retention rate can be increased by repeating charge and discharge several times. Turned out to be a decline.

Thus, in a battery using a solid electrolyte, realization of a lithium secondary battery having a high capacity retention has been demanded.

JP-A-8-180904 JP 2001-143687 A JP 2000-285910 A

  The present invention has been made to solve the above-described problems of the prior art, and provides a positive electrode or a negative electrode for a non-aqueous secondary battery that provides sufficient conductivity, provides high capacity, and excellent cycle characteristics. It is intended.

Further, the present invention is a lithium secondary battery comprising a positive electrode, a negative electrode, and a solid electrolyte, wherein the internal resistance of the battery is reduced, and the active material contained in the electrode and the solid electrolyte are being sintered or charged / discharged An object of the present invention is to provide a lithium secondary battery that suppresses the reduction in and has an excellent capacity retention rate.

  A first aspect of the present invention is an electrode for a non-aqueous secondary battery, characterized by comprising a deposit of a raw material powder comprising a metal oxide capable of inserting and releasing lithium ions and an inorganic solid electrolyte or a precursor thereof. is there.

  In the first aspect of the invention, the deposited body has a porosity of 15% or less, an electrical conductivity of 1 mS / cm or more, and a volume ratio of 1: 1 to 1 of the ratio of the metal oxide and the solid electrolyte contained in the positive electrode or the negative electrode. It is preferable that it consists of 9: 1.

  According to a second aspect of the present invention, at least one of a positive electrode containing a positive electrode active material and a negative electrode containing a negative electrode active material is composed of a metal oxide capable of inserting and releasing lithium ions and an inorganic solid electrolyte or a precursor thereof. It is a method for producing an electrode for a non-aqueous secondary battery, characterized in that it is formed by conveying ultrafine particles of raw material powder by an air stream and spraying and depositing on a substrate.

A third aspect of the present invention is a lithium secondary battery in which an electrolyte is interposed between a positive electrode active material layer and a negative electrode active material layer.
In the lithium secondary battery, the positive electrode active material layer and / or the negative electrode active material layer is formed of a deposited layer of an inorganic solid electrolyte in which conductive particles are dispersed and a metal oxide.

In the third aspect of the present invention, the conductive particles contained in the positive electrode active material layer and / or the negative electrode active material layer are preferably metal oxides having a conductivity at room temperature of 10 S / cm or more.
In the third aspect of the present invention, the conductive metal oxide particles contained in the positive electrode active material layer and / or the negative electrode active material layer are preferably non-reducing.
Furthermore, in the third aspect of the present invention, the metal oxide particles may be any one of sodium cobalt oxide, lithium-doped nickel oxide, aluminum-doped zinc oxide, antimony-doped tin oxide, tin-doped indium oxide, or a derivative thereof. It is preferable to consist of a plurality of species.

According to a fourth aspect of the present invention, at least one of a positive electrode containing a positive electrode active material and a negative electrode containing a negative electrode active material is composed of a metal oxide capable of inserting and releasing lithium ions and an inorganic solid electrolyte or a precursor thereof. A method for producing a lithium secondary battery, comprising using a positive electrode or a negative electrode formed by transporting ultrafine particles of raw material powder in an air stream and spraying and depositing on a substrate.

  An electrode for a non-aqueous secondary battery according to the present invention is a porous deposit containing a metal oxide, having a porosity of 15% or less, an electrical conductivity of 1 mS / cm or more, and a positive electrode or By setting the volume ratio of the metal oxide and solid electrolyte contained in the negative electrode to 1: 1 to 9: 1, the internal resistance of the battery can be reduced, the non-aqueous secondary battery having high capacity and excellent cycle characteristics Can provide.

Furthermore, according to the lithium secondary battery according to the present invention, the positive electrode active material layer and / or the negative electrode active material layer is formed of a deposited layer of a solid electrolyte in which conductive particles are dispersed and a metal oxide, Conductive metal oxide particles that do not exhibit reducibility are dispersed in the electrode active material layer, and by further limiting the raw material powder to be used, the impedance in the electrode can be lowered and the capacity retention rate can be improved. Is.

[First Embodiment]
According to the present invention, a positive electrode active material or a negative electrode active material having sufficient mechanical strength with high electrical conductivity can be realized by providing the solid electrolyte with ion conduction in the positive electrode or the negative electrode, thereby realizing strong bonding between the active materials. Can be realized. In addition, the porosity and the conductivity are indices indicating the binding force between the primary particles constituting the deposit, and it is sufficient to use an electrode material having a porosity and a conductivity within the range of the above invention. An electrode having mechanical strength is obtained. Further, by optimizing the amount of the solid electrolyte contained in the positive electrode or the negative electrode, ion conduction in the positive electrode or the negative electrode is facilitated.

  That is, the electrode of the present invention is a positive electrode or negative electrode for a non-aqueous secondary battery, which is a deposit of a raw material powder composed of a metal oxide capable of inserting and releasing lithium ions and a solid electrolyte or a precursor thereof. And

  Further, the positive electrode or the negative electrode for the non-aqueous secondary battery has a porosity of 15% or less and a conductivity of 1 mS / cm or more, and the metal oxide contained in the positive electrode or the negative electrode in the positive electrode or the negative electrode. The volume ratio of the ratio of the solid electrolyte is 1: 1 to 9: 1.

  According to the present invention, a positive electrode or a negative electrode for a non-aqueous secondary battery, which is a deposit of a raw material powder composed of a metal oxide capable of inserting and desorbing lithium ions and a solid electrolyte or a precursor thereof, is formed between active materials. A strong positive electrode or negative electrode with high electrical conductivity and sufficient mechanical strength can be provided.

  Moreover, since it consists only of solid substance substantially, the binding force between the primary particles which comprise a positive electrode or a negative electrode is reflected in a porosity and electroconductivity. Therefore, a deposit with a porosity of 15% or less and an electrical conductivity of 1 mS / cm or more has a strong binding force between primary particles, and even if the volume expands or contracts due to charge / discharge, the primary particles fall off or the electrodes collapse. Will not cause. Deposits having porosity and conductivity outside the above ranges are difficult to handle due to a decrease in the mechanical strength of the electrode, and at the same time, the internal resistance of the electrode is increased, resulting in deterioration of battery characteristics.

  Furthermore, by making the volume ratio of the metal oxide and solid electrolyte contained in the positive electrode or negative electrode 1: 1 to 9: 1, the ionic conduction in the positive electrode or negative electrode is facilitated, and the electrochemical reaction that occurs in the battery is prevented. make it easier.

  Hereinafter, embodiments of the electrode material which is the positive electrode or the negative electrode of the present invention will be described. The positive electrode or negative electrode of the present invention can be suitably used for a lithium secondary battery. Hereinafter, an embodiment in which the present invention is applied to a lithium secondary battery will be described.

  As the metal oxide capable of inserting and removing lithium ions used for the positive electrode of the present invention, any material of known lithium transition metal oxides can be used, but lithium cobaltate, lithium nickelate, lithium manganate, or It is preferable to use one or more of these derivatives.

  As the metal oxide capable of inserting and removing lithium ions used in the negative electrode of the present invention, any known material can be used, but lithium titanate, titanium oxide, lithium manganate, tin oxide, silicon oxide, lithium titanium It is preferable to use a composite oxide, iron oxide, niobium oxide, vanadium oxide, tungsten oxide, or a derivative thereof.

As the inorganic solid electrolyte contained in the positive electrode or the negative electrode of the present invention, any known material can be used, but Li _{1 + x + y} A _x Ti _2-x Si _y P _3-y O ₁₂ (A = A or Ga , 0 ≦ x ≦ 0.4, 0 <y ≦ 0.6), [(B _1/2 Li _1/2 ) _1−z C _z ] TiO ₃ (B = La, Pr, Nd, Sm, C = It is preferable to use an oxide having high ionic conductivity such as Sr or Ba, 0 ≦ z ≦ 0.5).

  The precursor of the substance is a substance that converts the substance by means of oxidation or the like, and specific examples include alkoxides and halides of the constituent elements of the substance.

  The electrode material of this embodiment can be used by further adding a conductive metal oxide. Such conductive metal oxide particles are characterized by not having reducibility, in particular sodium cobalt oxide, lithium-doped nickel oxide, aluminum-doped zinc oxide, antimony-doped tin oxide, tin-doped indium oxide, Or it consists of any 1 type or multiple types of those derivatives. By adding these metal oxides, excellent capacity retention characteristics as a battery can be realized.

  As a means for forming a film by densifying the oxide or inorganic material, a sintering method is generally used. However, a reaction between a metal oxide powder capable of inserting and releasing lithium ions and an inorganic solid electrolyte powder or heat The generation of stress is inevitable, and it becomes impossible to provide a positive electrode or a negative electrode with high electrical conductivity and sufficient mechanical strength, which achieves strong bonding between the active materials. Therefore, in the present invention, the positive electrode or the negative electrode is preferably produced by depositing raw material powder. Examples of the production method for depositing the raw material powder include a thermal spraying method and a gas deposition method in which the raw material powder is directly used as a solid bonded structure deposit. Further, as a method for depositing the constituent elements, there are methods such as sputtering and vacuum evaporation.

  More preferably, the metal oxide powder capable of inserting and removing lithium ions and the inorganic solid electrolyte powder are sprayed with fine particles having a particle size of about 1 μm or less by an accelerated air current to fix the lithium oxide powder onto the substrate in a predetermined shape. The aerosol deposition method is desirable from the viewpoint of manufacturing efficiency and energy saving. Details of this method will be described later.

The porosity of the deposit used for the obtained positive electrode or negative electrode is preferably 15% or less, more preferably 10% or less. While ensuring the conductivity of 1 mS / cm or more and the packing density of the positive electrode material, the movement of lithium ions in the positive electrode and the negative electrode can be further improved and the electrochemical reaction can be promoted.
The conductivity of the deposit used for the positive electrode or the negative electrode is preferably 1 mS / cm or more, more preferably 10 mS / cm or more. The binding force between the primary particles constituting the sintered body becomes stronger, and the mechanical strength of the electrode is further improved.

Moreover, the positive electrode or negative electrode of the present invention can constitute a secondary battery using a negative electrode or positive electrode paired therewith and a non-aqueous electrolyte.
As a non-aqueous electrolyte, a non-aqueous electrolyte solution in which a lithium compound such as LiPF ₆ is dissolved as an electrolyte in an organic solvent such as ethylene carbonate or dimethyl carbonate, or an organic solution in which a lithium compound is dissolved in a polymer or a lithium compound is dissolved in a polymer A solid polymer electrolyte or an inorganic solid electrolyte in which a solvent is held can be used.

(Deposition layer forming apparatus and method by aerosol deposition method)
Hereinafter, an apparatus for forming a deposited layer of an inorganic substance used in the present invention and a deposited layer forming method using the same will be described with reference to the drawings.

  FIG. 1 is a schematic view showing an example of an inorganic material deposition layer forming apparatus used for producing a lithium secondary battery. In FIG. 1, 11 is a nozzle, 12 is a substrate for forming a deposit layer of an inorganic substance, 13 is a deposition chamber, 14 is a deposit layer, 15 is a vacuum pump, 16 is a raw material container, and 17 is a raw material powder.

  In order to form a power generation element such as a positive electrode, a solid electrolyte layer, or a negative electrode as a deposition layer using ultrafine particles of an inorganic substance using this apparatus, a base material 12 is disposed in a deposition chamber 13, and a raw material powder 17 is filled in the raw material container. Next, a gas such as compressed air is press-fitted into the raw material container 16 by means such as a pump (not shown), and the raw material powder 17 in the raw material container 16 is dispersed in the gas and conveyed. From the nozzle 11 in the deposition chamber 13. The positive electrode, the solid electrolyte, or the negative electrode can be formed by ejecting toward the base material 14 and forming the deposited layer 14 of the raw material powder 17 on the base material 14.

  When forming a deposited layer by this apparatus, the nozzle 11 can be moved by a control device (not shown), and the deposited layer 14 having a large area can be formed by spraying while scanning the surface of the substrate 12. Further, the deposited layer 14 may be formed by a single injection, or may be formed by depositing ultrafine particles by a plurality of injections.

  The deposited layer formed by the above method is a dense layer having a relative density of 90% or more, and this deposited layer has a mechanical strength that is not broken even in handling of battery assembly.

  The film thickness of the deposited layer formed by one injection varies depending on the concentration of ultrafine particles in the carrier gas, the air volume of the carrier gas, and the scanning speed of the carrier gas, but is usually in the range of 0.1 to 10 μm. It is desirable to set to. If the film thickness falls below this range, it takes time to produce a battery having the required thickness, which is not practical. On the other hand, when the film thickness exceeds the above range, the formed film is difficult to be uniform, which causes a decrease in yield in the battery assembly process.

  In forming the deposited layer, the larger the difference in atmospheric pressure between the raw material container 16 and the deposition chamber 13, that is, the greater the gas velocity, the denser the deposited layer 14, which is an inorganic compound film, is formed. Strongly formed. Therefore, the pressure difference between the raw material container 16 and the deposition chamber 13 is preferably about 0.5 atm. If this atmospheric pressure difference is smaller than this, the fine particle conveyance speed is lowered, and it becomes difficult to form a dense and strong film. On the other hand, even if the pressure difference is larger than this, it is not necessary for improving the film forming efficiency. This pressure difference can be adjusted by pressurizing the gas to be injected and reducing the pressure by a vacuum pump connected to the deposition chamber 13.

  The air volume of the carrier gas is not particularly limited, but affects the amount of raw material powder fine particles that can be carried. That is, as the air volume is larger, a larger amount of raw material powder can be conveyed simultaneously, and the inorganic compound deposition rate can be improved.

  The temperature of the substrate 12, the deposition chamber 13, and the raw material container 16 during deposition is preferably in the range of room temperature to 500 ° C. Even if this temperature is cooled to room temperature or lower, it is not advantageous for film formation, and it is not preferable because it causes a loss of cooling energy. On the other hand, if this temperature exceeds 500 ° C., unless a means for eliminating the thermal stress after film formation is employed, residual stress is generated, leading to film destruction.

It is necessary to use ultrafine particles having a particle size of 3 μm or less, preferably 1 μm or less as a raw material powder for forming a deposited layer by the above method. When this particle size exceeds 3 μm, the deposited raw material powder film is not dense and the fracture strength is lowered, which is not suitable for battery production.
In addition, the material of the raw material powder is not particularly limited, and any inorganic fine particles can be used. As the particle shape, any shape such as a crushed particle shape and a spherical shape can be applied.

Further, the material of the base material for forming the deposited layer is not particularly limited, and any inorganic material can be applied.
Further, the substrate surface may be the surface of the substrate material itself or may be subjected to a surface treatment. This surface treatment is suitable for improving the adhesiveness to such an extent that the electrical conductivity of the surface is not impaired, and examples thereof include treatment such as plasma ion beam irradiation.

[Second Embodiment]
According to a second aspect of the present invention, in the lithium secondary battery in which an electrolyte is interposed between the positive electrode active material layer and the negative electrode active material layer, the positive electrode active material layer and / or the negative electrode active material layer have conductivity. It is a lithium secondary battery characterized in that it is formed of a deposited layer of an inorganic solid electrolyte in which conductive particles are dispersed and a metal oxide.

  According to the present invention, the formation of the positive electrode active material layer and / or the negative electrode active material layer is a deposition method by PVD, CVD, or aerosol deposition method, thereby reducing the reduction of the active material and the solid electrolyte by sintering and maintaining excellent capacity. The characteristics can be realized.

  The present invention is characterized in that the conductivity of particles having conductivity contained in the positive electrode active material layer and / or the negative electrode active material layer is a metal oxide of 10 S / cm or more.

  According to the present invention, battery internal resistance is reduced, and excellent capacity characteristics can be realized.

  The present invention is characterized in that the conductive metal oxide particles contained in the positive electrode active material layer and / or the negative electrode active material layer are not reducible, particularly sodium cobalt oxide, lithium doped nickel oxide. It is characterized by comprising any one or more of aluminum-doped zinc oxide, antimony-doped tin oxide, tin-doped indium oxide, or derivatives thereof. By limiting to these inorganic substances, excellent capacity retention characteristics can be realized.

  Hereinafter, embodiments of the lithium secondary battery of the present invention will be described. FIG. 2 is a cross-sectional view showing a configuration example of a lithium secondary battery according to the present invention. In FIG. 2, 21 is a positive electrode current collector, 22 is a positive electrode active material layer, 23 is an electrolyte, 24 is a negative electrode active material layer, and 25 is a negative electrode current collector. These power generation elements are encapsulated by a container 26. In the secondary battery, when a liquid electrolyte is used, the positive electrode active material layer and the negative electrode active material layer can be opposed to each other through a separator and impregnated with the liquid electrolyte.

  The positive electrode active material layer 22 is deposited so that a metal oxide serving as a positive electrode active material and a solid electrolyte are mixed, and is composed of conductive particles dispersed in the deposited layer. The negative electrode active material layer 24 is deposited such that a metal oxide having a lower charge / discharge potential than the charge / discharge potential of the positive electrode active material in the positive electrode active material layer 22 and a solid electrolyte are mixed as a negative electrode active material. The conductive layer is dispersed in the deposited layer.

  Examples of the metal oxide used for the positive electrode active material layer 22 and the negative electrode active material layer 24 include lithium manganese composite oxide, manganese dioxide, lithium nickel composite oxide, lithium cobalt composite oxide, lithium nickel cobalt composite oxide, and lithium. Examples thereof include vanadium composite oxide, lithium titanium composite oxide, titanium oxide, niobium oxide, vanadium oxide, tungsten oxide, and derivatives thereof. Here, there is no clear distinction between the positive electrode active material and the negative electrode active material, and the charge / discharge potentials of two kinds of compounds are compared with each other and a positive potential is used as a positive electrode, and a negative potential is used as a negative electrode. Thus, a battery having an arbitrary voltage can be configured.

Examples of the solid electrolyte used for the positive electrode active material layer 22 and the negative electrode active material layer 24 include Li ₂ O—B ₂ O ₃ —P ₂ O ₅ -based and Li ₂ O—B ₂ O ₃ —ZnO-based oxide-based non-oxides. amorphous solid _{electrolyte, LiI-Li 2 S-P} 2 S 5 and _{Li 3 PO 4 -Li 2 S-} Si 2 S sulfide-based amorphous solid electrolytes such as, _or like LiPO ₄ -Li 2 S-SiS An amorphous electrolyte in which a metal oxide and sulfide are mixed, such as Li _{1 + x + y} A _x Ti _2−x Si _y P _3−y O ₁₂ (A = A or Ga, 0 ≦ x ≦ 0.4, 0 <y ≦ 0.6), [(B _1/2 Li _1/2 ) _1−z C _z ] TiO ₃ (B = La, Pr, Nd, Sm, C = Sr or Ba, 0 ≦ z ≦ 0) _{.5), Li 3 PO (4-3} / 2w) N w (w <1) crystalline oxide-San窒such as Thing, and the like.

  The metal oxide and the solid electrolyte are mixed in a volume ratio of about 50:50 to 95: 5. When the amount of the metal oxide is too large, the contact area between the active material and the solid electrolyte becomes small, and the impedance in the electrode becomes small. Moreover, when there is too much quantity of solid electrolyte, there exists a problem that an active material filling rate will become low and a battery energy density will become small.

As the conductive particles dispersed in the solid electrolyte used for the positive electrode active material layer 22 and the negative electrode active material layer 24, one or two or more metal oxides having a conductivity of 10 S / cm or more are used. Are limited to metal oxides composed of one or more of sodium cobalt oxide, lithium-doped nickel oxide, aluminum-doped zinc oxide, antimony-doped tin oxide, tin-doped indium oxide and derivatives thereof.
This is because metal oxides such as SnO and TiO, which have a strong reducibility with a low oxidation number, base metals, or polymer conductors, some of the elements contained in the crystal structure of the active material or solid electrolyte are reduced. As a result, the crystal structure and the electrode structure can be easily collapsed, and the capacity retention rate is lowered by repeated charge and discharge several times.

  The conductive particles need to form a continuous network in the solid electrolyte in order to impart electronic conductivity. It is desirable that the conductive particles in the positive electrode active material layer 42 and the negative electrode active material layer 44 occupy 10% or more by volume ratio.

  The electrolyte 23 may be liquid or solid as long as it is a material having ion conductivity. The electrolyte 23 includes an organic electrolytic solution in which a desired electrolyte salt is dissolved in an organic solvent, a polymer solid electrolyte in which the electrolyte salt is dissolved in an ion conductive polymer material, a gel electrolyte in which these are combined, an inorganic electrolyte An inorganic solid electrolyte made of a material can be used. When an organic electrolyte is used for the electrolyte 23, a separator (not shown) for separating the positive electrode active material body 22 and the negative electrode active material body 24 is required.

  Examples of the organic solvent used in the organic electrolyte include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, gamma-butyrolactone, sulfolane, 1,2-dimethoxyethane, 1,3-dimethoxypropane, dimethyl ether, tetrahydrofuran, and 2-methyltetrahydrofuran. , One or a mixture of two or more solvents selected from dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate.

Examples of the electrolyte salt include lithium salts such as LiClO ₄ , LiBF ₄ , LiPF ₆ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , and LiN (C ₂ F ₅ SO ₂ ) ₂ .

  As the separator, for example, a nonwoven fabric made of polyolefin fibers or a microporous membrane made of polyolefin fibers can be used. Here, examples of the polyolefin fiber include polypropylene fiber and polyethylene fiber.

  Examples of the ion conductive polymer material include a polymer having an ethylene oxide skeleton typified by polyethylene oxide, a polymer having a propylene oxide skeleton typified by propylene oxide, a mixture or a copolymer thereof, and the like. In this case, the same electrolyte salt as the above-described organic electrolyte can be used.

Examples of the inorganic solid electrolyte include Li ₂ O—B ₂ O ₃ —P ₂ O ₅ -based, Li ₂ O—B ₂ O ₃ —ZnO-based oxide-based amorphous solid electrolyte, and LiI—Li ₂ S—, for example. Sulfide-based amorphous solid electrolytes such as P ₂ S ₅ and Li ₃ PO ₄ —Li ₂ S—Si ₂ S, or metal oxides and sulfides such as Li ₃ PO ₄ —Li ₂ S—SiS There amorphous electrolytes and _{mixed, Li 1 + x + y A} x Ti 2-x Si y P 3-y O 12 (A = A or Ga, 0 ≦ x ≦ 0.4,0 < y ≦ 0.6), [(B _1/2 Li _1/2 ) _1-z C _z ] TiO ₃ (B = La, Pr, Nd, Sm, C = Sr or Ba, 0 ≦ z ≦ 0.5), Li ₃ PO _{(4 −3 / 2w} ) N _w (w <1) and other crystalline oxides and oxynitrides.

  The positive electrode current collector 21 and the negative electrode current collector 25 are installed for collecting current from the positive electrode active material layer 22 and the negative electrode active material layer 24, and are made of, for example, a heat-solidified glass paste containing silver.

  When the above-described electrolyte is liquid or gel, it is caulked through an insulating packing, sealed, and stored in the sealed container 26.

The lithium secondary battery to which the present invention is applied is a secondary battery, even if it is a primary battery, as long as the positive electrode active material body and / or the negative electrode active material body is composed of a mixture with a solid electrolyte powder. There may be. The battery shape is not limited to a cylindrical shape, a square shape, a button shape, a coin shape, a flat shape, or the like.

The positive electrode was formed by an aerosol deposition method. Li _1.3 Al _0.3 Ti having a particle size distribution of D50 = 0.7 μm and Dtop = 2.8 μm as a solid electrolyte with respect to 60 parts by volume of LiCoO ₂ having a particle size distribution of D50 = 0.8 μm and Dtop = 2.3 μm. 40 parts by volume of _1.7 P ₃ O ₁₂ were mixed.
This mixed raw material powder is filled into the raw material container 16 of the aerosol deposition apparatus shown in FIG. Next, the raw material container 16 and the deposition chamber 13 that are in the middle of each other were depressurized to 1 torr by the vacuum pump 15. At this time, the temperature inside the deposition chamber 13 was set to room temperature. Further, compressed air is injected at a rate of 4 liters / min from the raw material container 16, and the raw material powder is dispersed and transported in the gas, and ejected from the nozzle 11 having an opening diameter of 5 mm × 0.5 mm in the deposition chamber 13. A raw material powder deposit 14 was formed on a substrate 12 which is an aluminum current collector having a thickness of 0.5 mm. At this time, by moving the substrate 12 at a speed of 0.1 mm / sec, LiCoO ₂ having a thickness of 30 μm and a porosity of 12% and Li _1.3 AlO _{. 3} was obtained Ti _1.7 P ₃ O ₁₂ cathode consisting of a volume of. The conductivity of this positive electrode was measured by the method described below and found to be 1.2 mS / cm.

  The conductivity of the sintered body is such that the electrode is baked with silver paste so as to substantially cover the deposited portion on the deposited body and without short-circuiting the facing current collector, and the current supply and voltage detection terminals are 2 on each side. Measurements were made for each book.

  The negative electrode to be paired with this was formed by the following method. 90 parts by mass of graphite powder having a particle size of about 1 μm and 70 parts by mass of an n-methyl-2-pyrrolidone solution of polyvinylidene fluoride (14% by mass) were mixed to obtain a uniform coating solution. This coating solution was applied onto the copper foil of the current collector, dried at 120 ° C. for 20 minutes, punched out to 10 × 10 mm, and made into a negative electrode integrated with the current collector.

  The electrolyte used was a solution in which 1 mol / L of lithium hexafluorophosphate was dissolved in a 1: 1 mixed solvent of propylene carbonate and dimethyl carbonate. The positive electrode and the negative electrode were laminated via a separator made of a polyethylene porous film, and after being accommodated in a battery can, the electrolyte solution was injected and sealed to produce a battery cell.

  When this battery cell was allowed to stand at room temperature for a whole day and night, a charge / discharge test was performed. The discharge capacity at the first cycle) × 100} was 90%.

(Comparative Example 1)
In Example 1 above, 95 parts by volume of LiCoO ₂ having a particle size distribution of D50 = 0.1 μm Dtop = 2.3 μm, and Li _1.3 Al having a particle size distribution of D50 = 0.1 μm Dtop = 2.3 μm as a solid electrolyte. _A positive electrode was prepared by the same method as in Example 1 except that _0.3 Ti _1.7 P ₃ O ₁₂ was used, and a positive electrode made of a LiCoO ₂ deposit with a porosity of 27% was obtained. The conductivity was 0.2 mS / cm. Furthermore, the discharge capacity at the first cycle of this battery cell was 6 mAh, and the capacity retention at the 50th cycle was 72%.

(Comparative Example 2)
In the first embodiment, with respect to LiCoO ₂ 95 parts by _{volume, Li 1.3 Al 0.3 Ti 1.7 P} 3 O 12 a except for using 5 parts by volume Example similarly to LiCoO ₂ of porosity 9 The positive electrode which consists of this deposit was obtained. The conductivity was 13 mS / cm. Furthermore, the discharge capacity of the battery cell at the first cycle was 0.2 mAh, and the capacity retention at the 50th cycle was 92%.

(Comparative Example 3)
In Example 1 above, a battery body was constructed and charged in the same manner as in Example 1 except that a molded body was prepared using the same raw material mixed powder and sintered at 900 ° C. to prepare a positive electrode sintered body. A discharge test was conducted. The produced battery cell was not charged / discharged.

A positive electrode was prepared by the same method as in Example 1 except that the temperature inside the deposition chamber 13 of Example 1 was set to 300 ° C., to obtain a positive electrode made of a LiCoO ₂ deposit having a porosity of 4%. Using this as the positive electrode, a battery cell was constructed in the same manner as in Example 1, and a charge / discharge test was conducted.

The conductivity of LiCoO ₂ was 10 mS / cm. Further, the discharge capacity of the battery cell at the first cycle was 6 mAh, and the capacity retention at the 50th cycle was 95%.

  As a result of forming the negative electrode by the aerosol deposition method and forming the secondary battery, almost the same effect was shown.

  From the above results, the higher the density and the higher the conductivity, the more the binding between the particles constituting the electrode progressed, the binding force between the particles increased, and the capacity retention rate was high. It is considered that even when the electrode repeatedly expands and contracts with charge and discharge, the primary particles are prevented from falling off and the electrode is prevented from collapsing due to the high binding force between the primary particles. Furthermore, it has been found that by optimizing the amount of the solid electrolyte contained in the positive electrode, a battery cell having a high active material packing density and a high capacity per unit volume can be produced.

LiCoO ₂ as a positive electrode active material, Li ₄ Ti ₅ O ₁₂ as a negative electrode active material, Li _1.3 Al _0.3 Ti _1.7 P ₃ O ₁₂ as a solid electrolyte mixed with these active materials, for positive electrode A battery using NaCo ₂ O ₄ as the conductive particles and Sb-doped SnO ₂ as the negative electrode conductive particles will be described below.

  All the raw materials used were commercially available. For any material, the particle size was adjusted by jet milling or heat treatment so that the D50 of the particle size was within the range of 0.8 ± 0.2 μm.

The positive electrode active material layer 22 is prepared by weighing and mixing LiCoO ₂ , Li _1.3 Al _0.3 Ti _1.7 P ₃ O _12, and NaCo ₂ O ₄₄ raw material powders in a volume ratio of 6: 3: 1. Then, this mixed powder was deposited on a glass substrate onto which a silver paste serving as the positive electrode current collector 21 was baked by an aerosol deposition method so as to be 10 mm × 10 mm. Specifically, the mixed raw material powder 17 is filled in the raw material container 16 of the aerosol deposition apparatus shown in FIG. Next, the raw material container 16 and the deposition chamber 13 that are in the middle of each other were decompressed to 1 torr by the vacuum pump 15. At this time, the temperature inside the deposition chamber 13 was set to room temperature. Further, compressed air is injected at a feed rate of 4 liters / min from the raw material container 16 and the raw material powder 17 is dispersed and transported in the gas. From the nozzle 11 having an opening diameter of 5 mm × 0.5 mm in the deposition chamber 13. The raw material powder deposit 14 was formed on the base material 12 which was a positive electrode current collector. At this time, the base material 12 is moved at a speed of 0.1 mm / sec, thereby causing LiCoO ₂ and Li _1.3 Al _0.3 Ti _1.7 P ₃ O ₁₂ and NaCo ₂ having a thickness of 30 μm and a porosity of 10%. A positive electrode composed of an O ₄ deposit 14 was obtained.

An electrolyte layer 23 was formed on the positive electrode active material layer 22 thus produced. Similarly, Li _1.3 Al _0.3 Ti _1.7 P ₃ O ₁₂ was also formed on the electrolyte layer 23 so as to cover the positive electrode active material layer 22.

Similarly, in the negative electrode active material layer 24, the volume ratio of Li ₄ Ti ₅ O ₁₂ , Li _1.3 Al _0.3 Ti _1.7 P ₃ O ₁₂ and Sb-doped SnO _{2 is set} to 6: 3: 1. Weighing and mixing were performed, and the mixed powder was formed on the electrolyte layer 23 by an aerosol deposition method so as to be 10 mm × 10 mm.

  A silver paste to be the negative electrode current collector 25 was baked on the negative electrode active material layer 24 to obtain a battery.

(Comparative Example 4)
The same positive electrode active material and negative electrode active material as in Example 3, a solid electrolyte mixed with the electrode active material, Li ₂ O—B ₂ O ₃ —ZnO glass, positive electrode conductive particles, nickel, and negative electrode conductive particles The batteries using tin are shown below. Commercially available Li ₂ O—B ₂ O ₃ —ZnO glass for solid electrolyte and nickel and tin for conductive particles were used.

The positive electrode active material layer 22 weighs LiCoO ₂ , Li ₂ O—B ₂ O ₃ —ZnO, and metal Ni so as to have a volume ratio of 6: 4: 1, and pressurizes the mixture to 10 mm × 10 mm. Molding was performed to obtain a formed body of the positive electrode active material layer 22. The negative electrode active material layer 24 weighs Li ₄ Ti ₅ O ₁₂ , Li ₂ O—B ₂ O ₃ —ZnO, and acetylene black in a volume ratio of 6: 4: 1, and this mixture becomes 10 mm × 10 mm. Thus, the negative electrode active material layer 24 was formed. The electrolyte layer weighed Li _1.3 Al _0.3 Ti _1.7 P ₃ O ₁₂ and Li ₂ O—B ₂ O ₃ —ZnO in a volume ratio, and the mixture was adjusted to 10 mm × 10 mm. The formed body of the electrolyte layer 23 was obtained by pressure molding. By sequentially laminating the positive electrode active material layer 22, the electrolyte layer 23, and the negative electrode active material layer 24, press-molding them again, applying a silver paste to be a positive electrode current collector and a negative electrode current collector, and firing at 550 ° C. A battery was obtained. The thickness of the produced battery was 2 mm.

(Comparative Example 5)
A battery was fabricated in the same manner as in Example 3, except that nickel was used as the positive electrode conductive particles and tin was used as the negative electrode conductive particles.
In the batteries of Comparative Example 4 and Comparative Example 5, the negative electrode active material layer 24 and the electrolyte layer 23, which were white, are blackened, and the metal elements in the crystals that supplement them are reduced. Conceivable.

(Comparative Example 6)
A battery was fabricated in the same manner as in Example 3 except that NiO was used as the conductive particles for accuracy and SnO ₂ was used as the conductive particles for the negative electrode.
The conductivity of the single conductive particles used in Comparative Example 6 was 1 S / cm or less at room temperature.

  A battery was fabricated in the same manner as in Example 1, except that Li-doped NiO was used as the positive electrode conductive particles and Al-doped ZnO was used as the negative electrode conductive particles.

  The conductivity of the conductive particles used in Example 3 and Example 4 was 10 S / cm or more at room temperature.

  The above-mentioned battery capacity retention rate was measured. The battery has a discharge capacity of 2.8V, a current value of 2mA, a constant current charge, left for 1 hour and discharged at a constant current value of 2mA to 2.0V. The capacity retention rate was calculated by comparing the capacity of the two.

  As a result, the battery of Example 3 had a discharge maintenance ratio of 95%, and the battery of Example 4 had a discharge maintenance ratio of 90%. In contrast, the battery of Comparative Example 4 had a discharge maintenance ratio of 70%, and the battery of Comparative Example 5 had a discharge maintenance ratio of 75%. In the battery of Comparative Example 6, the discharge capacity could not be measured because the discharge current was small. Thus, it can be seen that the metal oxide particles that do not exhibit conductive reducibility are dispersed in the electrode active material layer, thereby reducing the impedance in the electrode and improving the capacity retention.

In addition, this invention is not limited to what was shown to the said embodiment, In the range which does not deviate from the summary, it can implement by changing a suitable quantity.

It is the schematic which shows an example of the formation apparatus of the inorganic substance deposit body concerning this invention. It is sectional drawing which shows one Embodiment of the lithium secondary battery concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Nozzle 12 ... Base material 13 ... Deposition chamber 14 ... Deposition body 15 ... Vacuum pump 16 ... Raw material container 17 ... Raw material powder 21 ... Positive electrode collector 22 ... Positive electrode active material layer 23 ... Electrolyte layer 24 ... Negative electrode active material layer 25 ... Negative electrode current collector 27 ... Container

Claims (8)

  An electrode for a non-aqueous secondary battery comprising a deposit of a raw material powder comprising a metal oxide capable of inserting and releasing lithium ions and an inorganic solid electrolyte or a precursor thereof.   The deposited body has a porosity of 15% or less, an electrical conductivity of 1 mS / cm or more, and a volume ratio of 1: 1 to 9: 1 of the ratio of the metal oxide and the solid electrolyte contained in the positive electrode or the negative electrode. The electrode for non-aqueous secondary batteries according to claim 1.   At least one of the positive electrode containing the positive electrode active material and the negative electrode containing the negative electrode active material is an ultrafine particle of a raw material powder composed of a metal oxide capable of inserting and releasing lithium ions and an inorganic solid electrolyte or a precursor thereof, A method for producing an electrode material for a non-aqueous secondary battery, characterized in that the electrode material is formed by transporting in an air stream and spraying and depositing on a substrate. In a lithium secondary battery comprising an electrolyte interposed between a positive electrode active material layer and a negative electrode active material layer,
A lithium secondary battery, wherein the positive electrode active material layer and / or the negative electrode active material layer is formed of a deposited layer of an inorganic solid electrolyte in which conductive particles are dispersed and a metal oxide.   5. The lithium secondary battery according to claim 4, wherein the conductive particles contained in the positive electrode active material layer and / or the negative electrode active material layer are metal oxides having a conductivity at room temperature of 10 S / cm or more. Next battery.   The lithium secondary battery according to claim 4, wherein the conductive metal oxide particles contained in the positive electrode active material layer and / or the negative electrode active material layer are non-reducing.   The metal oxide particles are composed of one or more of sodium cobalt oxide, lithium-doped nickel oxide, aluminum-doped zinc oxide, antimony-doped tin oxide, tin-doped indium oxide, and derivatives thereof. Item 7. The lithium secondary battery according to Item 6. A raw material comprising at least one of a positive electrode containing a positive electrode active material and a negative electrode containing a negative electrode active material comprising a metal oxide capable of inserting and releasing lithium ions and an inorganic solid electrolyte or a precursor thereof and conductive particles A method for producing a lithium secondary battery, comprising using a positive electrode or a negative electrode formed by transporting ultrafine particles of powder in an air stream and spraying and depositing on a substrate.

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