JP5585847B2 - Method for producing electrode active material - Google Patents

Description

  The present invention relates to a method for producing an electrode active material used for a lithium secondary battery and other secondary batteries. Moreover, it is related with the electrode active material manufactured by this method, and its utilization.

In recent years, secondary batteries such as lithium secondary batteries (typically lithium ion batteries) and nickel metal hydride batteries have become increasingly important as power sources for vehicles or as power sources for personal computers and portable terminals. In particular, a lithium secondary battery that is lightweight and obtains a high energy density is preferably used as a high-output power source mounted on a vehicle.
By the way, as one measure for improving the performance of the secondary battery, miniaturization of electrode active material particles constituting the secondary battery can be mentioned. By reducing the particle size of the electrode active material (for example, the positive electrode active material of a lithium secondary battery), the filling properties of the electrode active material particles are improved. By improving the filling property, the active material density in the electrode (specifically, the electrode layer mainly composed of the electrode active material formed on the current collector) can be increased. Further, by reducing the particle size of the electrode active material, the surface area per unit mass of the active material is increased. For this reason, it is possible to improve the high rate characteristics, the rapid charge / discharge characteristics, and the like.

  Conventionally, various pulverization techniques are used to reduce the particle size of the electrode active material. For example, Patent Document 1 discloses a granulated molded article made of a mixture of lithium compound particles and cobalt oxide particles for the purpose of providing a positive electrode active material for a non-aqueous electrolyte secondary battery excellent in dispersibility and filling properties. A method for producing a positive electrode active material is disclosed, which is heated and fired at 800 to 1000 ° C. and then pulverized by a jet mill or the like.

JP 2003-123748 A

However, when excessive mechanical pulverization is performed using a conventional technique as described in the above-mentioned patent document, that is, a jet mill or other pulverizer, electrode active material particles having a desired fine particle size are obtained. On the other hand, a so-called mechanochemical effect is manifested during pulverization, which may change the crystal structure of the particles or reduce the crystallinity. In addition, when a wet pulverization process such as a bead mill is performed, components constituting the electrode active material may be eluted during the wet pulverization.
Such a change in crystal structure, a decrease in crystallinity, or a component elution from the active material particles is a cause of a decrease in performance of the electrode active material (for example, a positive electrode active material such as a lithium secondary battery) (for example, a decrease in charge / discharge capacity). This is not preferable.

  The present invention has been created to solve the above-described conventional problems related to miniaturization of the electrode active material, and the object of the present invention is an excessive factor that causes a decrease in performance as an electrode active material. It is to provide a method for producing an electrode active material (specifically, a positive electrode active material or a negative electrode active material) having a desired fine particle size without performing mechanical pulverization treatment. Another object of the present invention is to provide an electrode active material produced by the production method disclosed herein, characterized by using the provided electrode active material. A battery and a method for manufacturing the same are provided.

The present invention provides a method for producing an electrode active material of the following aspect.
That is, one manufacturing method disclosed here is a method for manufacturing an electrode active material for a secondary battery. Such a method is
(1) A temperature at which one or more raw material compounds for forming the electrode active material are dissolved or dispersed in an aqueous solvent and become insoluble in water at a predetermined lower critical solution temperature or higher. Preparing an aqueous raw material solution in which a responsive polymer is dissolved at a temperature equal to or lower than the lower critical solution temperature;
(2) raising the temperature of the prepared aqueous raw material liquid to a temperature range above the lower critical solution temperature, and generating insoluble aggregates in the heated aqueous raw material liquid;
(3) firing the generated insoluble aggregate to form the granular electrode active material (that is, a compound having an elemental composition that functions as an electrode active material);
Is included.
Here, the “temperature-responsive polymer” has a predetermined lower critical solution temperature (hereinafter also simply referred to as “LCST”) under atmospheric pressure conditions. Below the temperature, water-soluble (that is, hydrophilic) becomes prominent. On the other hand, when the LCST is exceeded, the polymer material exhibits a reversible phase transition behavior that becomes insoluble (that is, hydrophobic). .

The electrode active material manufacturing method disclosed herein is characterized in that an electrode active material having a target composition is prepared using the aqueous raw material liquid to which the temperature-responsive polymer is added.
Such an aqueous raw material liquid is one or more raw material compounds (for example, a positive electrode active material of a lithium secondary battery) for forming an electrode active material having a target composition when the temperature is below the LCST. In the case of forming a certain lithium transition metal composite oxide, a compound serving as a lithium source and a compound serving as one or more transition metal sources) are present in a dissolved or dispersed state in an aqueous solvent.
And this aqueous raw material liquid is heated (temperature rising) until it becomes more than said LCST. Thereby, the temperature-responsive polymer contained in the raw material liquid is insolubilized, and a fine aggregate (micelle) in a state in which the raw material compound coexisting in the aqueous raw material liquid is taken in can be generated. In other words, by generating the insoluble fine aggregate, it is possible to subdivide the raw material compound contained in the aqueous raw material liquid as the fine aggregate. That is, the size of the particles of the active material obtained by subsequent firing can be defined by generating fine aggregates containing the raw material compound.

  Next, according to the electrode active material manufacturing method disclosed herein, the generated insoluble aggregate is calcined (typically, the solvent in the aqueous raw material liquid containing the insoluble aggregate is removed by evaporation or the like to remove the insoluble aggregate. By firing the product after drying, a granular electrode active material having a particle size corresponding to the size of the generated aggregate can be produced. Therefore, in this production method, a granular electrode active material having a particle size corresponding to the size of the insoluble aggregate can be produced without performing excessive mechanical pulverization treatment. Therefore, the crystal structure of the active material particles due to the mechanochemical effect is obtained. The target electrode active material particles can be produced while avoiding the influence and performance degradation as an active material.

In a preferred embodiment of the electrode active material manufacturing method disclosed herein, the temperature-responsive polymer is poly (N-alkylacrylamide), poly (N-vinylalkylamide), polyvinylalkylether, poly (2- Alkyl-2-oxazoline) and at least one selected from the group consisting of polyethylene glycol-polypropylene glycol block copolymers. For example, a suitable example of poly (N-alkylacrylamide) is poly (N-isopropylacrylamide), and a preferred example of polyvinylalkyl ether is polyvinyl methyl ether.
These are typical temperature-responsive polymers, and their temperature-responsive behavior has been investigated in detail, and the lower critical solution temperature can be controlled. For example, since poly (N-isopropylacrylamide) and polyvinyl methyl ether have a lower critical solution temperature slightly higher than normal temperature, temperature control can be easily performed, and the production of the intended granular electrode active material becomes easier. .

In a preferred embodiment of the electrode active material manufacturing method disclosed herein, the aqueous raw material liquid contains a water-soluble gelling agent. Therefore, the steps shown in (2) and (3) above are:
(2) 'The aqueous raw material liquid containing the gelling agent is heated to a temperature range exceeding the lower critical solution temperature, and the aqueous solvent is evaporated from the aqueous raw material liquid in the temperature range to produce the insoluble aggregates generated above. Forming a gelled body comprising,
(3) 'forming the electrode active material by firing such a gelled body;
Is included.

In the electrode active material manufacturing method disclosed herein, as the gelling agent, glycolic acid (C ₂ H ₄ O ₃ ), malic acid (C ₄ H ₆ O ₅ ), citric acid (C ₆ H ₈ O ₇ ) Hydroxycarboxylic acid or a derivative thereof can be preferably used. By adding the gelling agent, the raw material compound forms a salt with the gelling agent (precursor of the target electrode active material) and becomes a more reactive ion in a uniformly dispersed state in the aqueous raw material liquid. Can be retained. Therefore, the insoluble aggregates formed by raising the temperature of the aqueous raw material liquid to the above temperature range can have a more uniform composition. Next, the gelled body is fired. The salt of the raw material compound and the gelling agent can be converted into a desired electrode active material by firing at a relatively low temperature.
According to the electrode active material manufacturing method disclosed herein, the raw material compound in a uniform mixed state can be converted to the target composite oxide by a reaction at a relatively low temperature, and the solid solution of the raw material metal element has sufficiently advanced. An active material can be obtained. Therefore, an electrode active material capable of having a high charge / discharge capacity as a battery is provided.

As described above, the electrode active material manufacturing method disclosed herein is an electrode active material having a desired composition by liquid phase mixing in a state where a raw material compound that can be dissolved or dispersed in an aqueous solvent is dissolved or dispersed in the aqueous solvent. The present invention can be applied to the production of an electrode active material including a step of forming.
In a preferred aspect of the electrode active material manufacturing method disclosed herein, the electrode active material to be manufactured is a positive electrode active material of a lithium secondary battery. As a positive electrode active material for such a lithium secondary battery, lithium transition metal composite oxidation comprising at least one transition metal element of nickel (Ni), cobalt (Co) and manganese (Mn) as a constituent element Things. Among other things, the general formula:
_{Li (Li a Mn x Co y} Ni z) O 2
(Where a, x, y, and z are positive real numbers satisfying a + x + y + z = 1)
And a positive electrode active material mainly composed of a lithium-excess type transition metal composite oxide represented by Alternatively, a negative electrode active material mainly composed of a silicon oxide represented by the general formula: SiO _x (where x is a real number satisfying 0 <x <2) can be given. According to the production method disclosed herein, the capacity per unit mass of these high-capacity active materials can be further expanded.

As apparent from the above description, in the production method disclosed herein, insoluble aggregates generated by raising the temperature of the aqueous raw material liquid are recovered (typically, the aqueous solvent is evaporated to obtain a solid residue. Insoluble aggregates are collected) and fired to produce an electrode active material having a desired particle size.
Therefore, according to the production method disclosed herein, the size of the electrode active material particles after firing according to the size of the insoluble aggregates (micelles) produced while suppressing the aggregation of the particles of the electrode active material ( Particle size) can be defined. That is, typically, a granular electrode active material having a small particle size distribution (preferably having a substantially uniform particle size) can be suitably produced without performing pulverization after firing. That is, according to the manufacturing method of this configuration, by utilizing the phase transition behavior of the temperature-responsive polymer, the electrode active material particles in a well-dispersed state in which excessive aggregation is suppressed are further refined. It can be produced as a granular electrode active material.

The present invention also provides a lithium secondary battery comprising a positive electrode active material produced by any of the production methods disclosed herein as a positive electrode or a negative electrode.
As described above, the lithium secondary battery disclosed herein has a high capacity by including an electrode active material having a fine particle size in which high crystallinity is maintained without being subjected to excessive mechanical pulverization. Good electrical conductivity can be realized. For this reason, it has performance suitable as a battery used as a power source (power source) for driving a motor mounted on a vehicle that is particularly required to be charged and discharged at a high rate.
Therefore, according to this invention, the vehicle provided with the lithium secondary battery disclosed here is provided. In particular, a vehicle (for example, an automobile) including the lithium secondary battery as a power source (typically, a power source of a hybrid vehicle or an electric vehicle) is provided.

It is a process flow figure showing a manufacturing process of a granular electrode active material concerning one embodiment of the present invention. It is a figure which illustrates typically the state of the aqueous raw material liquid in the temperature below the lower critical solution temperature prepared in the manufacturing method disclosed here. It is a figure which illustrates typically the state (formation | generation of an insoluble aggregate) of the aqueous | water-based raw material liquid at the time of heating up to the temperature range exceeding a lower critical solution temperature in the manufacturing method disclosed here. It is a figure which shows typically the lithium secondary battery which concerns on one Embodiment of this invention. It is a front view which shows typically an example of a wound electrode body. It is sectional drawing which shows typically the structure of the single battery with which an assembled battery is equipped. It is a side view which shows typically the vehicle (automobile) provided with the lithium secondary battery which concerns on one Embodiment of this invention. It is a figure which illustrates the particle size distribution of the granular electrode active material obtained by the manufacturing method disclosed here and the granular electrode active material obtained by the conventional manufacturing method.

Hereinafter, preferred embodiments of the present invention will be described. Note that matters other than matters specifically mentioned in the present specification and necessary for the implementation of the present invention can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.
In the present specification, the “electrode active material” is a term including a positive electrode active material used on the positive electrode side and a negative electrode active material used on the negative electrode side. Here, the active material refers to a substance (compound) involved in power storage on the positive electrode side or the negative electrode side. That is, it refers to a substance involved in electron emission or capture during battery charge / discharge.
Further, in this specification, the “lithium secondary battery” refers to a battery in which lithium ions in the electrolyte are responsible for charge transfer, and is called a so-called lithium ion battery (or lithium ion secondary battery), a lithium polymer battery, or the like. These are typical examples included in the “lithium secondary battery” mentioned here.

According to the manufacturing method disclosed herein, as described above, a granular electrode active material for a secondary battery having a particle size corresponding to the size of the insoluble aggregate can be manufactured.
Hereinafter, as a preferred embodiment of the present invention, a case where a lithium transition metal composite oxide is produced as an electrode active material will be exemplified, and the present invention will be described in detail.
In the production method disclosed herein, as shown in the process flow diagram of FIG. 1, first, (1) one or more raw material compounds for forming the electrode active material are dissolved or dissolved in an aqueous solvent. An aqueous raw material liquid is prepared in which a temperature-responsive polymer that is dispersed and further insoluble in water at a predetermined lower critical solution temperature or higher is dissolved in the aqueous solvent at a temperature lower than the lower critical solution temperature.

<Raw compound>
As such a raw material compound, a water-soluble compound including a constituent element for constituting a desired electrode active material can be used. When producing a lithium transition metal composite oxide as an electrode active material, typically, a lithium source and one or more transition metal element sources are prepared as raw material compounds.

The lithium source compound that is one of the raw material compounds is not particularly limited as long as it can be dissolved (or dispersed) in an aqueous solvent, and various lithium compounds can be used. For example, lithium hydroxide, lithium carbonate, lithium sulfate, lithium nitrate, lithium peroxide, lithium phosphate, lithium oxalate, lithium acetate, and lithium iodide can be used as a lithium source compound that can be dissolved or dispersed in an aqueous solvent. it can. Particularly preferred examples include hydrates such as lithium acetate dihydrate [Li (CH ₃ COO) · 2H ₂ O].

  Further, the transition metal element source is not particularly limited, but as a suitable specific example, the lithium transition metal composite oxide may be nickel (Ni), cobalt (Co), or manganese (Mn). In the case of an oxide that also contains a nickel source, a cobalt source and a manganese source are preferred starting materials. As the compound including such a transition metal element, compounds such as hydroxides, oxides, various salts (for example, carbonates), halides (for example, fluorides) of various transition metal elements that can be dissolved in an aqueous solvent are selected. Can be done.

For example, examples of the nickel source compound include compounds such as nickel acetate, nickel oxalate, nickel carbonate, nickel oxide, nickel sulfate, nickel nitrate, nickel hydroxide, and nickel oxyhydroxide. A particularly preferable example is nickel acetate (II) tetrahydrate [Ni (CH ₃ COO) ₂ .4H ₂ O].

Examples of the cobalt source compound include compounds such as cobalt acetate, cobalt oxalate, cobalt carbonate, cobalt oxide, cobalt sulfate, cobalt nitrate, cobalt hydroxide, and cobalt oxyhydroxide. A particularly preferred example is cobalt (II) acetate tetrahydrate [Co (CH ₃ COO) ₂ .4H ₂ O].

Furthermore, examples of the manganese source compound include compounds such as manganese acetate, manganese oxalate, manganese carbonate, manganese oxide, manganese sulfate, manganese nitrate, manganese hydroxide, and manganese oxyhydroxide. Particularly preferable examples include manganese acetate (II) tetrahydrate [Mn (CH ₃ COO) ₂ .4H ₂ O] or manganese sulfate.

  The transition metal constituting the lithium transition metal composite oxide includes at least one transition metal element selected from the group consisting of nickel (Ni), cobalt (Co), and manganese (Mn), A metal element of two or more kinds of metal elements (that is, a transition metal element and / or a typical metal element other than the main constituent metal element) may be contained in a proportion smaller than the molar ratio of the constituent metal elements. Examples of such metal elements include aluminum (Al), iron (Fe), chromium (Cr), vanadium (V), magnesium (Mg), titanium (Ti), zirconium (Zr), niobium (Nb), molybdenum ( Mo, tungsten (W), copper (Cu), zinc (Zn), gallium (Ga), indium (In), tin (Sn), lanthanum (La), cerium (Ce), and the like.

<Temperature responsive polymer>
Furthermore, in the present invention, a temperature-responsive polymer is used to define the particle size of the electrode active material.
The temperature-responsive polymer has a lower critical solution temperature (LCST) at a temperature lower than the boiling point of the aqueous solvent, is water-soluble below a predetermined LCST, and is insoluble in water at a temperature above a predetermined LCST. At least one selected from those can be used. For example, two or more kinds can be used in combination. A typical example of such a temperature-responsive polymer is a polymer having the chemical structure shown below.

(A) Poly (N-alkylacrylamide)

(B) Poly (N-vinylalkylamide)

(C) Polyvinyl alkyl ether

(D) Poly (2-alkyl-2-oxazoline)

In addition to the chemical structures shown above, the following polymers can also be suitably used.
(E) Polyethylene glycol-polypropylene glycol block copolymer Among them, it is preferable to use a temperature-responsive polymer having an LCST higher than room temperature (for example, 25 ° C) by about 5 ° C to 30 ° C, more preferably about 5 ° C to 15 ° C. This is preferable because it is simple in terms of production. As such a temperature-responsive polymer, for example, (a) poly (N-isopropylacrylamide) whose functional group R in poly (N-alkylacrylamide) is i-Pr (isopropyl group) (LCST: about 32 ° C.) ), (C) polyvinyl methyl ether (LCST: about 34 ° C.) in which the functional group R in the polyvinyl alkyl ether is Me (methyl group).

<Preparation of aqueous raw material liquid>
Each starting material is then weighed. The mixing ratio of each starting material can be appropriately adjusted according to the composition ratio of the desired lithium-containing transition metal composite oxide. Then, each starting material is mixed with an aqueous solvent and sufficiently diffused or permeated. Typically, water (including distilled water and deionized water) can be used as the aqueous solvent. Alcohol etc. may be contained as needed. Furthermore, an aqueous raw material liquid can be prepared by dissolving the temperature-responsive polymer in an aqueous solvent at a temperature equal to or lower than the lower critical solution temperature.
As shown conceptually in FIG. 2, the aqueous raw material liquid at a temperature lower than the lower critical dissolution temperature is obtained by dispersing or dissolving the starting raw material 102 and the temperature-responsive polymer 104 in an aqueous solvent (for example, water). It exists in a mixed state.
Here, in order to promote the gelation described later, a gelling agent may be added together with the above starting material and the temperature-responsive polymer. As the gelling agent, a nonionic water-soluble organic compound not containing metal ions, for example, an organic compound having a carboxylic acid group not containing metal ions can be used. More specifically, glycolic acid (C ₂ H ₄ O ₃ ), malic acid (C ₄ H ₆ O ₅ ), citric acid (C ₆ H ₈ O ₇ ), hydroxycarboxylic acid or a derivative thereof is preferably used. Can do. The addition amount of a gelling agent is not specifically limited, It is good to adjust suitably so that a desired gel form may be exhibited.
In the mixing, stirring (including kneading and pulverization) may be performed as necessary. The apparatus used for mixing is not particularly limited. For example, by using a planetary mixer, a planetary stirrer, a desper, a ball mill, a kneader, a mixer, etc., the above raw material mixture can be uniformly diffused or permeated and stabilized. A mixed state can be formed.

<Formation of insoluble aggregates>
Next, in the production method disclosed herein, (2) the prepared aqueous raw material liquid is heated (heated up) to a temperature range above the lower critical solution temperature to generate insoluble aggregates in the aqueous raw material liquid. . In this state, the temperature-responsive polymer 104 in the aqueous raw material liquid is insolubilized and, as shown in FIG. 3, minute insoluble aggregates (micelles) in a state where the raw material compound 102 is incorporated in the aqueous raw material liquid. 110 is generated. In other words, the raw material compound 102 contained in the aqueous raw material liquid can be classified into the form of the fine aggregate 110 by generating the insoluble fine aggregate 110. That is, the generation of the fine aggregate 110 containing the raw material compound 102 defines the size of the active material particles obtained by subsequent firing.
As described above, in a state where the gelling agent is added to the aqueous raw material liquid, the raw material compound forms a salt with the gelling agent and becomes a more reactive ion in a more uniformly dispersed state in the aqueous raw material liquid. Can be retained. Therefore, the insoluble aggregate formed by raising the temperature of the aqueous raw material liquid to a temperature range above the lower critical solution temperature in a state containing the gelling agent has a more uniform composition.

<Gelification>
And in the preferable form of the manufacturing method disclosed here, the said aqueous | water-based raw material liquid is gelatinized, and the gelled body containing said insoluble essential substance 110 is formed. In the gelation, the gelation can be promoted by heating (drying) the raw material mixture at a temperature at which the aqueous solvent evaporates. The heating temperature in this case is not particularly limited, but is preferably heated in a temperature range from room temperature to 100 ° C. (typically 20 to 90 ° C., preferably 50 to 90 ° C., approximately 80 ± 5 ° C.). By doing so, a part (or all) of the aqueous solvent is volatilized, and the sol state in the particle dispersion state can be changed to the gel state having no fluidity.
The heating time may be appropriately adjusted while confirming the dry state of the raw material mixture. In addition, as a heating method, any heating (drying) means such as hot air, vacuum, infrared rays, far-infrared rays and the like can be suitably used. Furthermore, the atmosphere at the time of heating may be put in an atmosphere of an inert gas such as nitrogen gas, or in a sealed container as needed depending on the type of solvent and starting material used.
Gelation can also be promoted by adjusting the pH of the aqueous solvent to about 1-2 by adding an acid or the like.

<Baking>
Next, (3) firing will be described. The insoluble aggregate remaining after evaporation of the aqueous solvent of the aqueous raw material liquid or the gelled body containing the insoluble aggregate is fired. The firing is desirably performed in an oxidizing atmosphere, for example, the air or an atmosphere richer in oxygen than the air. The firing temperature is a temperature of 1000 ° C. or less, and it is typically preferable to heat the material to 700 to 900 ° C., for example, about 800 ° C. for firing. Further, the firing time is not particularly limited, but after the temperature has been raised to the set temperature, firing can be performed in the temperature range for about 5 to 24 hours.
By performing such heat treatment, the target lithium transition metal oxide precursor can be converted into a positive electrode active material. The positive electrode active material thus obtained is in the form of particles having a particle size corresponding to the size of the insoluble aggregate. Although its size varies depending on the composition of the target lithium transition metal oxide, the type of temperature-responsive polymer, other manufacturing conditions, etc., it cannot be generally stated, but it is on the order of nm to several μm. It can be obtained as particles.

  In addition, when the obtained particles are bonded by agglomeration or sintering after firing to form a lump, light pulverization can be performed as necessary. Moreover, you may make it obtain the granular electrode active material which has a desired average particle diameter and / or particle size distribution by grind | pulverizing, granulating, and classifying a baked material by a suitable means.

As described above, the present invention has been described in detail for the case of producing a lithium transition metal composite oxide as an electrode active material. As a positive electrode active material for a lithium secondary battery suitably produced by the production method disclosed herein, for example, LiCoO _{2, LiNiO 2, LiMn 2 O} 4 and the like.
Furthermore, a lithium-excess type transition metal composite oxide in which Li is arranged at a transition metal site, which has attracted attention as a positive electrode active material capable of increasing the capacity density per weight, is also a suitable production target. A typical example of this type of active material is a solid solution of Li (Li _1/3 Mn _2/3 ) O ₂ and Li (NiCoMn) O ₂ having the general formula:
_{Li (Li a Mn x Co y} Ni z) O 2
An electrode active material mainly composed of a lithium-excess type transition metal composite oxide represented by Here, a, x, y, and z in the formula are typically positive real numbers that satisfy a + x + y + z = 1.
Moreover, the positive electrode active material for a lithium secondary battery that is preferably manufactured by the manufacturing method disclosed herein is not limited to the above-described lithium transition metal composite oxide (including lithium-excess transition metal composite oxide). For example, it may be a polyanionic compound represented by the general formula: LiMAO ₄ . M in such formula is typically one or more elements (typically one or two) including at least one metal element selected from the group consisting of Fe, Co, Ni and Mn. A metal element of a species or more). That is, it contains at least one metal element selected from the group consisting of Fe, Co, Ni, and Mn, but allows the presence of other minor additive elements that can be contained in small amounts (even if such minor additive elements are not present). Good.) A in the above formula is typically one or more elements selected from the group consisting of P, Si, S and V.

Further, the electrode active material of the present invention is not limited to the positive electrode active material. For example, as the electrode active material, various metal compounds (for example, metal oxides) suitable as a negative electrode active material of a lithium secondary battery, Specifically, for example, a metal compound (preferably a metal oxide) containing Si, Ge, Sn, Pb, Al, Ga, In, As, Sb, Bi, or the like as a constituent metal element may be used.
In particular, a metal oxide mainly composed of silicon oxide as defined by the general formula: SiO _x can be preferably used. Here, x in the formula is typically a real number satisfying 0 <x <2, and preferably 0 <x <0.6. A commercially available powder material made of silicon oxide such as SiO can be suitably used. By utilizing such a silicon oxide as a negative electrode active material, a lithium secondary battery having a particularly high charge / discharge capacity can be obtained.

  The granular electrode active material manufactured by the manufacturing method disclosed here can be suitably used as the active material for the positive electrode or the negative electrode of the battery, similarly to the conventional electrode active material. Except for using such an electrode active material, various types of secondary batteries can be constructed by employing the same materials and processes as in the past. For example, a lithium secondary battery can be constructed by employing an excess lithium-containing transition metal composite oxide produced by the production method disclosed herein as a positive electrode active material.

Hereinafter, lithium provided with a positive electrode active material made of an excess lithium-containing transition metal composite oxide represented by the above general formula: Li (Li _a Mn _x Co _y Ni _z ) O ₂ produced by the production method disclosed herein One embodiment of a secondary battery (lithium ion battery) will be described, but the usage pattern of the electrode active material disclosed herein is not intended to be limited thereto.

  The lithium ion battery according to this embodiment is characterized by using the granular electrode active material as a negative electrode active material. Therefore, as long as the object of the present invention can be realized, the contents, materials, and compositions of other battery constituent materials and members are not particularly limited, and those similar to those of conventional lithium ion batteries can be used.

As the positive electrode, here particulate obtained by the process disclosed in the positive electrode active material _{(Li (Li a Mn x Co} y Ni z) O 2), it is optionally used and the binder (binder) A material in which a positive electrode active material layer (also referred to as a positive electrode composite material layer) is formed by adhering to a positive electrode current collector as a positive electrode composite material together with a conductive auxiliary material or the like can be preferably used.

As the positive electrode current collector, a rod-like body, a plate-like body, a foil-like body, a net-like body or the like mainly composed of aluminum, nickel, titanium, stainless steel, or the like can be used. As the positive electrode active material, in addition to the above-described excess type lithium transition metal composite oxide, a layered lithium transition metal composite oxide that can be used for a positive electrode of a general lithium ion battery, a spinel structure lithium transition metal composite An oxide, a polyanion compound having an olivine structure, and the like can be preferably used. Typical examples of such an active material include lithium transition metal oxides such as lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), and lithium manganate (LiMn ₂ O ₄ ). Moreover, the general formula: the compound represented by Limao ₄ and the like. M in such a formula is one or more elements (typically one or more metals) including at least one metal element selected from the group consisting of Fe, Co, Ni, and Mn. Element). That is, it contains at least one metal element selected from the group consisting of Fe, Co, Ni, and Mn, but allows the presence of other minor additive elements that can be contained in small amounts (even if such minor additive elements are not present). Good.) A in the above formula is preferably one or more elements selected from the group consisting of P, Si, S and V. LiFePO _{4 Examples, LiFeSiO 4, LiCoPO 4, LiCoSiO} 4, LiFe 0.5 Co 0.5 PO 4, LiFe 0.5 Co 0.5 SiO 4, LiMnPO 4, LiMnSiO 4, LiNiPO 4, LiNiSiO 4 is particularly It is mentioned as a preferable polyanion type compound.

As the binder, for example, commonly used polyvinylidene fluoride (PVdF), a water-soluble acrylic binder, or the like can be used. Examples of the conductive material include carbon black (for example, acetylene black), carbon material such as graphite powder, or conductive metal powder such as nickel powder. Although it does not specifically limit, the usage-amount of the electrically conductive material with respect to 100 mass parts of positive electrode active materials can be 1-20 mass parts (preferably 5-15 mass parts), for example. Moreover, the usage-amount of a binder with respect to 100 mass parts of positive electrode active materials can be 0.5-10 mass parts, for example.
Then, a powdery material containing the positive electrode active material and the conductive auxiliary material as described above is dispersed in an appropriate dispersion medium together with an appropriate binder and kneaded to obtain a paste-like positive electrode mixture (hereinafter referred to as “positive electrode mixture paste”). "). A positive electrode for a lithium ion battery can be produced by applying an appropriate amount of this positive electrode mixture paste onto a positive electrode current collector, followed by drying and pressing.

  On the other hand, as the negative electrode current collector, a rod-like body, a plate-like body, a foil-like body, a net-like body or the like mainly composed of copper, nickel, titanium, stainless steel, or the like can be used. Examples of the binder include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR), and the like. As the conductive auxiliary material, a carbon material such as carbon black similar to the conventional one can be preferably used.

  Examples of the negative electrode active material include various metal compounds (for example, metal oxides), specifically, Si, Ge, Sn, Pb, Al, Ga, In, As, Sb, Bi, and the like as constituent metal elements. It may be a metal compound (preferably a metal oxide). Of course, this negative electrode active material can also be manufactured by the manufacturing method disclosed here. Moreover, for example, a granular negative electrode active material excellent in conductivity whose surface is sufficiently covered with a carbon film can be suitably used. In this case, the conductive auxiliary material is not contained in the negative electrode active material layer, or the content of the conductive auxiliary material can be reduced as compared with the conventional case. Although it does not limit, the usage-amount of the conductive auxiliary material with respect to 100 mass parts of negative electrode active materials to be used is about 1-30 mass parts (preferably about 2-20 mass parts, for example, about 5-10 mass parts), for example. can do. A conductive auxiliary material may be previously contained in the electrode active material supply material described above.

  Then, the granular negative electrode active material and, if necessary, a powdery material containing a conductive auxiliary material together with an appropriate binder (binder), an appropriate dispersion medium (for example, N-methylpyrrolidone: an organic solvent such as NMP or water) A paste-like negative electrode mixture (hereinafter referred to as “negative electrode mixture paste”) is prepared by dispersing and kneading in such an aqueous solvent. A negative electrode for a lithium ion battery can be produced by applying an appropriate amount of this negative electrode mixture paste onto a negative electrode current collector, followed by drying and pressing.

  As the electrolyte interposed between the positive electrode and the negative electrode, a liquid electrolyte containing a nonaqueous solvent and a lithium salt soluble in the solvent is preferably used. It may be a solid (gel) electrolyte in which a polymer is added to such a liquid electrolyte. As the non-aqueous solvent, aprotic solvents such as carbonates, esters, ethers, nitriles, sulfones, and lactones can be used. For example, ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, Generally lithium ion batteries such as 2-methyltetrahydrofuran, dioxane, 1,3-dioxolane, diethylene glycol dimethyl ether, ethylene glycol dimethyl ether, acetonitrile, propionitrile, nitromethane, N, N-dimethylformamide, dimethyl sulfoxide, sulfolane, γ-butyrolactone, etc. One kind or two or more kinds selected from non-aqueous solvents known as those that can be used in the electrolyte can be used.

Lithium salts include LiPF ₆ , LiBF ₄ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiC (SO ₂ CF ₃ ) ₃ , LiClO _4, etc., one or more selected from various lithium salts known to be capable of functioning as a supporting electrolyte in the electrolyte of a lithium ion battery can be used. The concentration of the lithium salt is not particularly limited, and can be the same as, for example, the electrolyte used in a conventional lithium ion battery. Usually, a non-aqueous electrolyte containing a supporting electrolyte (lithium salt) at a concentration of about 0.1 mol / L to 5 mol / L (for example, about 0.8 mol / L to 1.5 mol / L) is preferably used. it can.

A lithium ion battery is constructed by housing the positive electrode and the negative electrode together with an electrolyte in a suitable container (a metal or resin casing, a bag made of a laminate film, or the like). In a typical configuration of the lithium ion battery disclosed herein, a separator is interposed between the positive electrode and the negative electrode. As a separator, the thing similar to the separator used for a general lithium ion battery can be used, and it does not specifically limit. For example, a porous sheet made of a resin such as polyethylene (PE), polypropylene (PP), polyester, cellulose, or polyamide, a nonwoven fabric, or the like can be used. Note that in a lithium ion battery (lithium polymer battery) using a solid electrolyte, the electrolyte may also serve as a separator.
The shape (outer shape of the container) of the lithium secondary battery is not particularly limited, and may be, for example, a cylindrical shape, a square shape, a coin shape, or the like.

Hereinafter, a lithium-ion battery including a wound electrode body and an on-vehicle assembled battery (battery pack) constructed using the battery as a constituent part (unit cell) are manufactured by the manufacturing method disclosed herein. A more specific aspect of the lithium secondary battery using the negative electrode active material will be described, but the present invention is not intended to be limited to such an embodiment.
In addition, in the following drawings, the same code | symbol is attached | subjected to the member and site | part which show | plays the same effect | action, and the overlapping description may be abbreviate | omitted or simplified. In addition, the dimensional relationship (length, width, thickness, etc.) in each drawing does not reflect the actual dimensional relationship.

As shown in FIG. 4, the unit cell 12 used as a component of the assembled battery 10 according to the present embodiment typically has a predetermined battery constituent material (correct An active body for each negative electrode, a current collector for each positive and negative electrode, a separator, etc.) and a container for housing the electrode body and an appropriate electrolyte.
The assembled battery 10 disclosed here includes a predetermined number (typically 10 or more, preferably about 10 to 30, for example, 20) of unit cells 12 having the same shape. The unit cell 12 includes a container 14 having a shape (a flat box shape in this embodiment) that can accommodate a flat wound electrode body to be described later. The size of each part of the unit cell 12 (for example, the outer shape such as the thickness in the stacking direction) may vary due to a dimensional error at the time of manufacturing the container 14 to be used.
The container 14 is provided with a positive electrode terminal 15 electrically connected to the positive electrode of the wound electrode body and a negative electrode terminal 16 electrically connected to the negative electrode of the electrode body. As shown in the figure, one positive terminal 15 and the other negative terminal 16 are electrically connected by a connector 17 between adjacent unit cells 12. Thus, the assembled battery 10 of the desired voltage is constructed | assembled by connecting each cell 12 in series.
In addition, the container 14 can be provided with a safety valve 13 or the like for venting gas generated inside the container in the same manner as a conventional unit cell container. Since the configuration of the container 14 itself does not characterize the present invention, a detailed description is omitted.

The material of the container 14 is not particularly limited as long as it is the same as that used in the conventional unit cell. For example, a container made of metal (for example, aluminum, steel, etc.), a container made of synthetic resin (for example, polyolefin resin such as polypropylene, high melting point resin such as polyethylene terephthalate, polytetrafluoroethylene, polyamide resin, etc.) is preferably used. be able to. The container 14 according to the present embodiment is made of, for example, aluminum.
As shown in FIG. 5 and FIG. 6, the unit cell 12 has a sheet-like positive electrode 32 (hereinafter also referred to as “positive electrode sheet 32”) and a sheet-like negative electrode 34 (hereinafter, referred to as a wound electrode body of a normal lithium ion battery). Are laminated together with a total of two sheet-like separators 36 (hereinafter also referred to as “separator sheets 36”), and the positive electrode sheet 32 and the negative electrode sheet 34 are wound while being slightly shifted. Then, a flat wound electrode body 30 is provided which is produced by crushing and curling the obtained wound body from the side surface direction.

  As shown in FIG. 5, as a result of being wound while being slightly shifted as described above in the lateral direction with respect to the winding direction of the wound electrode body 30, a part of the ends of the positive electrode sheet 32 and the negative electrode sheet 34 respectively. It protrudes outward from the wound core portion 31 (that is, the portion where the positive electrode active material layer forming portion of the positive electrode sheet 32, the negative electrode active material layer forming portion of the negative electrode sheet 34, and the separator sheet 36 are closely wound). A positive electrode lead terminal 32B and a negative electrode lead terminal 34B are attached to the protruding portion (that is, the non-forming portion of the positive electrode active material layer) 32A and the protruding portion (that is, the non-forming portion of the negative electrode active material layer) 34A. The lead terminals 32B and 34B are electrically connected to the positive terminal 15 and the negative terminal 16 described above, respectively.

The material and the member itself constituting the wound electrode body 30 having the above configuration employ a negative electrode active material with a carbon coating obtained by the production method disclosed herein (for example, SiO _{x of the} above general formula) as the negative electrode active material. Otherwise, it may be the same as the electrode body of the conventional lithium ion battery, and there is no particular limitation.
The positive electrode sheet 32 is formed by applying a positive electrode active material layer for a lithium secondary battery on a long positive electrode current collector (for example, a long aluminum foil). In the present embodiment, a sheet-like positive electrode current collector having a shape that can be preferably used for the lithium secondary battery (unit cell) 12 including the wound electrode body 30 is used. For example, a positive electrode prepared in advance using an aluminum foil having a length of 2 m to 4 m (for example, 2.7 m), a width of 8 cm to 12 cm (for example, 10 cm), and a thickness of about 5 μm to 30 μm (for example, 10 μm to 20 μm) as a current collector. A positive electrode active material layer is formed by applying a composite paste to the surface of the current collector. The paste can be suitably applied to the surface of the positive electrode current collector by using an appropriate application device such as a gravure coater, a slit coater, a die coater, or a comma coater.

  After applying the paste, the positive electrode active material layer is formed by drying and compressing (pressing) the solvent (typically water) contained in the paste. As the compression method, a conventionally known compression method such as a roll press method or a flat plate press method can be employed. In adjusting the thickness of the positive electrode active material layer, the thickness may be measured with a film thickness measuring instrument, and the press pressure may be adjusted to compress a plurality of times until a desired thickness is obtained.

  Meanwhile, the negative electrode sheet 34 may be formed by applying a negative electrode active material layer for a lithium secondary battery on a long negative electrode current collector. As the negative electrode current collector, a conductive member made of a highly conductive metal, such as copper, can be used. In the present embodiment, a sheet-like negative electrode current collector having a shape that can be preferably used for the lithium secondary battery (unit cell) 12 including the wound electrode body 30 is used. For example, a copper foil having a length of 2 m to 4 m (for example, 2.9 m), a width of 8 cm to 12 cm (for example, 10 cm), and a thickness of about 5 μm to 30 μm (for example, 10 μm to 20 μm) is used as the negative electrode current collector. A negative electrode mixture paste prepared by adding and dispersing or dissolving an active material and a binder in an appropriate solvent (water, an organic solvent and a mixed solvent thereof) (for example, 80 to 90% by mass of a negative electrode active material, conductivity aid) 3 to 15% by mass of the material and 3 to 10% by mass of the binder) can be applied, and the solvent can be dried and compressed.

Moreover, as a suitable separator sheet 36 used between the positive / negative electrode sheets 32 and 34, what was comprised with the porous polyolefin resin is illustrated. For example, a porous separator sheet made of a synthetic resin (for example, made of polyolefin such as polyethylene) having a length of 2 m to 4 m (for example, 3.1 m), a width of 8 cm to 12 cm (for example, 11 cm), and a thickness of about 5 μm to 30 μm (for example, 25 μm). It can be preferably used.
In the case of a lithium secondary battery (lithium polymer battery) using a solid electrolyte or a gel electrolyte as an electrolyte, a separator is unnecessary (that is, in this case, the electrolyte itself can function as a separator). possible.

The obtained flat wound electrode body 30 is accommodated in the container 14 such that the winding axis is laid down as shown in FIG. 6 and an appropriate supporting salt (for example, a lithium salt such as LiPF ₆ ). As a mixed solvent of diethyl carbonate (DEC) and ethylene carbonate (EC) containing an appropriate amount (for example, concentration of 1M) (for example, DEC: EC may be in the range of 1: 9 to 9: 1 by volume ratio). A single battery 12 is constructed by injecting a nonaqueous electrolyte (electrolytic solution) and sealing.

  As shown in FIG. 4, the plurality of cells 12 having the same shape constructed as described above are inverted one by one so that the positive terminals 15 and the negative terminals 16 are alternately arranged, and the container 14 Wide surfaces (that is, surfaces corresponding to flat surfaces of a wound electrode body 30 to be described later housed in the container 14) are arranged in an opposing direction. A cooling plate 11 having a predetermined shape is disposed in close contact with the wide surface of the container 14 between the arranged unit cells 12 and both outsides in the unit cell arrangement direction (stacking direction). The cooling plate 11 functions as a heat radiating member for efficiently dissipating heat generated in each unit cell during use. Preferably, the cooling plate 11 is a cooling fluid (typically air) between the unit cells 12. It has a frame shape that can be introduced. Alternatively, a cooling plate 11 made of a metal with good thermal conductivity or lightweight and hard polypropylene or other synthetic resin is suitable.

  A pair of end plates 18 are disposed on the outer side of the cooling plate 11 arranged on both outsides of the unit cells 12 and the cooling plates 11 (hereinafter collectively referred to as “single cell group”). , 19 are arranged. One or a plurality of sheet-like spacer members 40 as length adjusting means may be sandwiched between the cooling plate 11 and the end plate 18 disposed on one outside of the unit cell group. . The constituent material of the spacer member 40 is not particularly limited, and various materials (metal material, resin material, ceramic material, etc.) can be used as long as the thickness adjusting function described later can be exhibited. A metal material or a resin material is preferably used from the viewpoint of durability against impact or the like. For example, a lightweight polyolefin resin spacer member 40 can be preferably used.

  Then, the single cell group, the spacer member 40 and the end plates 18 and 19 arranged in the stacking direction of the single cells 12 in this way are attached so as to bridge both the end plates 18 and 19. The band 21 is restrained by a predetermined restraining pressure P in the stacking direction. More specifically, as shown in FIG. 4, by tightening and fixing the end portion of the restraining band 21 to the end plate 18 with screws 22, the unit cell group has a predetermined restraining pressure P (for example, the container 14 of the container 14) in the arrangement direction. The surface pressure received by the wall surface is constrained to be about 0.1 MPa to 10 MPa. In the assembled battery 10 constrained by the constraining pressure P, the constraining pressure is also applied to the wound electrode body 30 inside the container 14 of each unit cell 12, and the gas generated in the container 14 is generated inside the wound electrode body 30. It is possible to prevent the battery performance from being deteriorated by being stored in (for example, between the positive electrode sheet 32 and the negative electrode sheet 34).

In addition, the unit cell 12 and the assembled battery 10 may have performance suitable as a battery mounted on a vehicle, in particular, a high capacity maintenance rate and excellent durability. Further, as the electrode active material, a negative electrode active material made of a metal oxide such as SiO _x, or a positive electrode active material made of an excess type lithium transition metal composite oxide such as Li (Li _a Mn _x Co _y Ni _z ) O ₂ Can also be adopted, and higher capacity can be realized.
Further, according to the present invention, as shown in FIG. 7, a vehicle 1 including a lithium ion battery 12 (assembled battery 10) is provided. In particular, a vehicle (for example, an automobile) including the battery 12 as a power source (typically, a power source of a hybrid vehicle or an electric vehicle) is provided.

  Hereinafter, as some specific examples, a lithium secondary battery (here, a lithium ion battery) is constructed using a positive electrode including a granular electrode active material manufactured by the manufacturing method disclosed herein, Performance evaluation was performed.

<Synthesis of Granular Electrode Active Material According to Examples>
In the following procedure, a positive electrode active material for a lithium secondary battery represented by the general formula: Li (Li _0.2 Mn _0.54 Co _0.13 Ni _0.13 ) O ₂ was synthesized.
That is, lithium acetate dihydrate [Li (CH ₃ COO) 2H ₂ O] as a lithium source and manganese acetate (II) tetrahydrate [Mn (CH ₃ COO) _2. and 4H ₂ O], cobalt acetate as a cobalt source (II) · tetrahydrate _{[Co (CH 3 COO) 2 ·} 4H 2 O ], nickel acetate (II) · tetrahydrate as nickel source [Ni Starting materials for constituting a composite oxide having the above composition ratio including (CH ₃ COO) ₂ .4H ₂ O] were prepared. This starting material is placed in a 1 L beaker together with glycolic acid as a gelling agent and poly (N-isopropylacrylamide) as a temperature-responsive polymer (hereinafter sometimes referred to as “PNIPAM”), and ion-exchanged water. Was mixed and dissolved at 20 ° C. below the lower critical solution temperature to prepare an aqueous raw material solution.

Next, nitric acid was added to the aqueous raw material liquid to adjust the pH to 1.75, and the mixture was heated to 80 ° C. exceeding the lower critical solution temperature with stirring to produce insoluble aggregates in the aqueous raw material liquid. While continuing stirring at the temperature, water was evaporated to gel the aqueous raw material liquid to obtain a precursor.
The obtained precursor was collected and fired at 800 ° C. to synthesize the granular electrode active material according to Example 1.
<Synthesis of Granular Electrode Active Material According to Comparative Example>
The granular electrode active material which concerns on a comparative example was synthesize | combined by the same process using the material similar to the said Example except not adding PNIPAM as a temperature-responsive polymer.

<Comparison of average particle size>
About the granular electrode active material obtained by the Example and the comparative example, the particle size distribution was investigated by the laser diffraction method. The result (particle size distribution) is shown in FIG.
As is apparent from FIG. 8, the active material of the example obtained by adding the temperature-responsive polymer to the aqueous raw material liquid is the same as the active material of the comparative example obtained without using the temperature-responsive polymer. In comparison, the particle size distribution was shifted to the small particle diameter side, and it was confirmed that finer particles were obtained overall. That is, by adding the temperature-responsive polymer to the aqueous raw material liquid as described above, the particle size can be reduced in the synthesis process without applying extra external force to the active material after synthesis. This shows that it is possible to produce a granular active material that is smaller and crystallinity is not impaired.

<Evaluation cell construction and electrochemical property evaluation>
An evaluation cell was constructed using the granular electrode active materials obtained in Examples and Comparative Examples.
That is, the maximum firing temperature was set to about 1000 ° C. in an argon gas atmosphere for each active material, and firing was performed at that temperature for about 6 hours. The sample was preliminarily fired for about 1 to 5 hours in the temperature range of 200 ° C. to 300 ° C. and then heated to the maximum firing temperature. Thereby, an unnecessary hydroxy group of PVA can be eliminated.

Each active material after the firing treatment thus obtained was crushed and classified with a 100 mesh sieve to obtain a test electrode active material. Test electrodes were prepared using the obtained 100-mesh under electrode active material particles. That is, the active material, graphite particles, and PVDF were mixed with N-methylpyrrolidone so that the mass ratio thereof was 85: 10: 5 to prepare a slurry-like composition (paste). This composition was applied to a copper foil having a thickness of 10 μm (manufactured by Japan Foil) and dried to form an active material layer having a thickness of 25 μm on one surface of the copper foil. This was pressed so that the total electrode density including the copper foil and the active material layer was 1.2 mg / cm ^2, and then punched into a circle having a diameter of 16 mm to produce an evaluation electrode.

A metal lithium foil having a diameter of 15 mm and a thickness of 0.15 mm was used as the counter electrode. As the separator, a porous polyolefin sheet having a diameter of 22 mm and a thickness of 0.02 mm was used. As the electrolytic solution, a solution obtained by dissolving LiPF ₆ as a lithium salt at a concentration of about 1 mol / L in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 3: 7 was used. .
These constituent elements were incorporated into a stainless steel container to construct a coin cell for evaluation having a general shape with a thickness of 2 mm and a diameter of 32 mm (so-called 2032 type).

  Two types of coin cells prepared as described above (hereinafter, the cell prepared using the electrode active material of the example is referred to as “cell of example”, and the cell prepared using the electrode active material of comparative example is referred to as “comparative example of Test electrode until the interelectrode voltage reaches 0.01 V at a constant current of 0.1 C (1 C, that is, a current value that is 0.1 times the current value that can be fully charged and discharged in 1 hour). The operation of inserting Li into the electrode and the operation of desorbing Li from the test electrode until the interelectrode voltage reached 1.2 V at a constant current of 0.1 C were performed. The value obtained by dividing the Li insertion capacity by the active material mass (Li insertion capacity per unit mass of the active material: mAh / g) at this time, and the value obtained by dividing the Li desorption capacity by the active material mass (active material). Li desorption capacity per unit mass of the substance: mAh / g) was determined as the initial discharge capacity. The value obtained by dividing the initial discharge capacity per unit mass of the active material by the initial charge capacity was defined as the initial coulomb efficiency (%). Specifically, it was determined from the following formula: (initial discharge capacity) / (initial charge capacity) × 100. The results are shown in Table 1.

  As is apparent from Table 1, the Example cell produced by the production method disclosed herein had a significantly higher initial Coulomb efficiency (87. 8) than that of the Comparative Example cell (82.9%). 1%). This is because the active material particles are miniaturized and the packing properties of the electrode active material particles are improved, the density of the active material in the electrode is increased, and the surface area per unit mass of the active material is reduced by the miniaturization of the electrode active material. It is thought to be derived from the increase. That is, the manufacturing method disclosed here is expected to improve the high-rate characteristics, rapid charge / discharge characteristics, etc. of the lithium secondary battery.

  As mentioned above, although this invention was demonstrated by suitable embodiment, such description is not a limitation matter and of course various modifications are possible.

  According to the production method disclosed herein, an electrode active material having a fine particle size can be provided without requiring an excessive mechanical pulverization treatment. This electrode active material has excellent Coulomb characteristics because there is no change in crystal structure or crystallinity due to grinding, and there is no risk of elution of components from the active material particles, so performance degradation (for example, reduction in charge / discharge capacity) is suppressed. Will be. Therefore, by using such an electrode active material, it is possible to provide a secondary battery such as a lithium secondary battery having high capacity and good durability. By adopting the electrode active material manufactured by the manufacturing method disclosed here from such characteristics, for example, a vehicle-mounted secondary battery (particularly a vehicle-mounted lithium secondary battery) used as a power source for driving a vehicle. Can be provided.

1 vehicle 10 assembled battery 12 lithium secondary battery (single cell)
15 positive electrode terminal 16 negative electrode terminal 30 wound electrode body 32 positive electrode sheet 34 negative electrode sheet 102 raw material compound 104 temperature-responsive polymer 110 insoluble aggregate

Claims (8)

A method for producing a granular electrode active material for a secondary battery, comprising:
An aqueous raw material liquid in which one or two or more raw material compounds for forming the electrode active material are dissolved or dispersed in an aqueous solvent, and has a high temperature responsiveness that becomes insoluble in water at a predetermined lower critical solution temperature or higher. Preparing an aqueous raw material solution in which molecules are dissolved at a temperature equal to or lower than the lower critical solution temperature;
Raising the temperature of the prepared aqueous raw material liquid to a temperature range above the lower critical solution temperature, and generating insoluble aggregates in the heated aqueous raw material liquid;
Firing the generated insoluble aggregates to form the electrode active material;
Manufacturing method.   The temperature-responsive polymer is composed of poly (N-alkylacrylamide), poly (N-vinylalkylamide), polyvinylalkylether, poly (2-alkyl-2-oxazoline), and polyethylene glycol-polypropylene glycol block copolymer. The manufacturing method of Claim 1 which is at least 1 sort (s) selected from the group which consists of.   The manufacturing method according to claim 2, wherein the temperature-responsive polymer is poly (N-isopropylacrylamide) and / or polyvinyl methyl ether. The aqueous raw material liquid contains a water-soluble gelling agent,
The aqueous raw material liquid containing the gelling agent is heated to the temperature range, and the aqueous solvent is evaporated from the aqueous raw material liquid in the temperature range to form a gelled body containing the generated insoluble aggregates.
The manufacturing method according to any one of claims 1 to 3, wherein the electrode active material is formed by firing the gelled body. The electrode active material is a lithium-excess type represented by the general formula: Li (Li _a Mn _x Co _y Ni _z ) O ₂ (where a, x, y, and z are positive real numbers satisfying a + x + y + z = 1). The manufacturing method in any one of Claims 1-4 comprised mainly by the transition metal complex oxide. 5. The electrode active material according to claim 1, wherein the electrode active material is mainly composed of a silicon oxide represented by a general formula: SiO _x (where x is a real number satisfying 0 <x <2). The manufacturing method as described.   A lithium secondary battery comprising, as a positive electrode or a negative electrode, an electrode active material produced by the production method according to claim 1.   A vehicle comprising the lithium secondary battery according to claim 7.

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