JP5445841B2 - Method for producing electrode active material - Google Patents

Description

  The present invention relates to a method for producing an electrode active material (typically a positive electrode active material) used for a lithium secondary battery. In detail, it is related with the manufacturing method of the electrode active material which has an amorphous structure.

In recent years, secondary batteries such as lithium secondary batteries and nickel metal hydride batteries have become increasingly important as power sources mounted on vehicles using electricity as a drive source, or power sources mounted on personal computers, portable terminals, and other electrical products. . In particular, a lithium secondary battery (typically a lithium ion battery) that is lightweight and obtains a high energy density is expected to be preferably used as a high-output power source mounted on a vehicle.
A lithium secondary battery includes an electrode having a configuration in which a material (electrode active material) capable of reversibly occluding and releasing lithium ions serving as a charge carrier is held in a conductive member (electrode current collector), and further increases energy. In order to achieve higher density and higher output, electrode active material materials are being studied. For example, as a positive electrode active material used for a positive electrode of a lithium secondary battery, a lithium-containing composite oxide having a layered structure, a spinel structure, or the like containing lithium (Li) and at least one transition metal element can be given.

As a conventional technique related to the method for producing an electrode active material for a lithium secondary battery, Patent Document 1 discloses production of LiM _x Mn _2−x O ₄ (0 <x <2) having a spinel crystal structure. A method is disclosed. In this method, a raw material is dissolved in a volatile solvent, and is sprayed and deposited on a substrate from a nozzle to which a voltage is applied. Patent Documents 2 and 3 disclose oxides made amorphous (amorphized) as electrode active materials for lithium secondary batteries. In batteries using an oxide with an amorphous structure as the electrode active material, the insertion position of lithium ions is irregular and there are no restrictions on the crystal structure, so the amount of lithium ion occlusion can be increased and the capacity is further increased. Alternatively, it is expected as an electrode active material that can realize high energy density.

JP 2002-260656 A JP-A-6-275277 JP 2005-135866 A

  By the way, as a method for producing the lithium-containing composite oxide having the amorphous structure, as described in Patent Documents 2 and 3, a powdery compound as a raw material is mixed so as to have a predetermined composition, Examples thereof include a method of quenching after firing at a temperature at which the raw material mixture melts (melting and quenching method), a method of sputtering using a ground and mixed raw material mixture as a powder target (sputtering method), and the like. However, since the composite oxide having an amorphous structure manufactured using a conventionally known method has a particle size of the order of μm, it is difficult to improve the battery capacity. In addition, there are problems in terms of manufacturing cost and workability, such as including extremely high temperature firing in the manufacturing process.

  The present invention has been made in view of such points, and an object of the present invention is to provide a lithium secondary battery made of a complex oxide having an amorphous structure with a smaller particle size by firing at a low temperature range that has never been achieved. It is to provide a method of manufacturing an electrode active material for use. Another object of the present invention is to provide a lithium secondary battery including a positive electrode using an electrode active material manufactured by such a manufacturing method.

In order to achieve the above object, according to the present invention, a composite oxide having an amorphous structure, lithium, at least one transition metal element, and at least one element capable of forming glass in the form of an oxide together with oxygen, A method for producing an electrode active material for a lithium secondary battery comprising a composite oxide is provided.
The manufacturing method disclosed here is: 1) Dissolving a starting material for constituting the composite oxide in an organic solvent including at least a lithium source, the transition metal element source, and the glass-forming element source. And 2) heating the raw material mixture to volatilize the organic solvent, and 3) firing the raw material mixture after volatilizing the organic solvent. Features.

In the present specification, the “lithium secondary battery” refers to a secondary battery that uses lithium ions as electrolyte ions and is charged and discharged by movement of lithium ions between the positive and negative electrodes. In general, a secondary battery referred to as a lithium ion battery is a typical example included in the lithium secondary battery in this specification.
In this specification, the “electrode active material” refers to a substance capable of reversibly occluding and releasing (typically inserting and removing) chemical species (that is, lithium ions) serving as charge carriers in a secondary battery. Say.

A lithium-containing composite oxide having a layered structure or a spinel structure is superior in lithium secondary battery using the oxide as an electrode active material (typically, a positive electrode active material) as the crystallinity is higher and the particle size is finer. It is known that the battery characteristics (for example, cycle characteristics, high rate characteristics) are good. On the other hand, since the composite oxide obtained by the production method according to the present invention has an amorphous structure (amorphous structure), it does not have the specific crystal structure as described above. However, complex oxides with an amorphous structure can store a large amount of lithium ions because the insertion positions of lithium ions are irregular and there are no restrictions on the crystal structure. It is expected as an electrode active material that can be realized.
In the manufacturing method provided by the present invention, glass can be formed in the form of an oxide together with lithium, at least one transition metal element, and oxygen by using a method different from the conventional method such as a melt quenching method or a sputtering method. Producing an electrode active material for a lithium secondary battery comprising a complex oxide having an amorphous structure containing at least one element (for example, B, Al, Si, P, Ge, Te, Ga, Bi, etc.) It is.

  Such a production method includes first dissolving a starting material for constituting a composite oxide containing at least a lithium source, the transition metal element source, and the glass-forming element source in an organic solvent to form a raw material mixture. Prepare and heat the raw material mixture to volatilize (evaporate) the organic solvent (typically dry the raw material mixture). And the process of baking the raw material mixture after volatilizing an organic solvent is further included. According to the manufacturing method including the above steps, the particle size is smaller than the particle size of the composite oxide having an amorphous structure obtained by the conventional manufacturing method (for example, an average particle size of about 3 μm in the melt quenching method) (scanning electron microscope). The average particle diameter based on observation is typically 1 μm or less, for example, 100 nm to 500 nm, preferably about 200 to 300 nm), and a composite oxide having an amorphous structure is obtained. Therefore, according to the present invention, it is possible to provide an electrode active material for a lithium secondary battery made of a composite oxide capable of realizing a high capacity or high energy density of the lithium secondary battery.

A preferable embodiment of the production method disclosed herein includes a step of holding the raw material mixture after volatilizing the organic solvent at a temperature of 100 ° C. or less after the volatilization step.
After the raw material mixture is heated to volatilize the organic solvent, it is maintained at a temperature of 100 ° C. or lower (typically, the temperature of the heated raw material mixture is once lowered to 100 ° C. or lower). The content of Li ₃ PO ₄ that does not contribute to charge / discharge can be reduced from the obtained composite oxide. As a result, an electrode active material for a lithium secondary battery capable of constructing a lithium secondary battery having a higher battery capacity or higher energy density can be provided.

In another preferred embodiment of the production method disclosed herein, in the volatilization step, the raw material mixture is heated at a temperature that is at least higher than 100 ° C. and lower than the maximum firing temperature in the firing step.
In the volatilization step, heating is performed at a temperature at which the organic solvent contained in the raw material mixture volatilizes (the boiling point of the organic solvent to be used or a temperature in the vicinity thereof, for example, boiling point ± 20 ° C.). The heating temperature is preferably higher than 100 ° C. and lower than the maximum baking temperature in the subsequent baking step. As a result, the organic solvent can be volatilized more effectively.

Preferably, in the firing step, the maximum firing temperature is set to 400 ° C. or lower.
Since the firing is possible at such a lower maximum firing temperature (referring to the firing temperature set in an apparatus such as a heating furnace), the lithium secondary composed of a composite oxide having a target amorphous structure more efficiently. An electrode active material for a battery can be produced.

In another preferred embodiment, the raw material mixture has the general formula:
Li _a MX _b O _c (1)
(A, b and c in the formula (1) are
0 <a ≦ 2.5,
0 <b ≦ 3,
c = {a + (valence of M) + b × (valence of X)} / 2
Is a number that satisfies all
M is at least one transition metal element, and X is at least one element capable of forming glass in the form of an oxide with oxygen. )
To prepare a composite oxide represented by

In another preferable aspect, the M element includes one or more elements selected from the group consisting of manganese (Mn), nickel (Ni), cobalt (Co), and iron (Fe). . Particularly preferably, the M element is one or more elements selected from the group consisting of manganese (Mn), nickel (Ni), cobalt (Co), and iron (Fe).
An electrode active material made of a composite oxide containing such a transition metal element can occlude more charge carriers (lithium). As a result, a higher capacity lithium secondary battery can be provided.

In another embodiment, the element X includes one or more elements selected from the group consisting of boron (B), phosphorus (P), and silicon (Si). Particularly preferably, the X element is one or more elements selected from the group consisting of boron (B), phosphorus (P), and silicon (Si).
Boron (B), phosphorus (P), and silicon (Si) are elements capable of forming glass in the form of oxides (B ₂ O ₃ , P ₂ O ₅ , and SiO ₂ ) together with oxygen. Therefore, by preparing a raw material mixture using an element source of such an element, an amorphous structure composite oxide having no specific crystal structure can be suitably obtained.

Further, preferably, a hydrate of a compound containing the element is used as the lithium source and / or the transition metal element source.
When a raw material mixture is prepared using a hydrate, the raw material mixture changes into a gel when the above-mentioned organic solvent is volatilized and the solidified raw material mixture is maintained at a temperature of 100 ° C. or lower. Thereby, the electrode active material for lithium secondary batteries which can implement | achieve a higher capacity | capacitance or a high energy density can be provided.

In another preferred embodiment of the production method provided by the present invention, the method further includes a step of pulverizing the fired product obtained after the firing step.
By pulverizing and granulating the fired product, the specific surface area of the composite oxide having an amorphous structure can be increased. Thereby, further increase in capacity of the lithium secondary battery is realized.

Further, according to any of the production methods disclosed herein, the composite oxide having an amorphous structure is characterized in that the average particle diameter based on observation with a scanning electron microscope is 1 μm or less.
By using an electrode active material composed of a composite oxide having an amorphous structure with a fine particle diameter, typically having an average particle diameter of 1 μm or less (for example, 100 nm to 500 nm, preferably about 200 to 300 nm), a high battery capacity is achieved. A lithium secondary battery having the above can be provided.

Moreover, this invention provides a lithium secondary battery provided with the positive electrode which uses the said electrode active material for lithium secondary batteries as another side surface which implement | achieves the said objective.
Furthermore, according to this invention, the vehicle provided with the lithium secondary battery disclosed here is provided. The lithium secondary battery provided by the present invention may exhibit performance (for example, high capacity or high energy density) suitable as a power source for a battery mounted on a vehicle. Therefore, the lithium secondary battery disclosed herein can be suitably used as a power source for a motor (electric motor) mounted on a vehicle such as an automobile equipped with an electric motor such as a hybrid vehicle or an electric vehicle.

It is a perspective view which shows typically the external shape of the lithium secondary battery which concerns on one Embodiment. It is the II-II sectional view taken on the line in FIG. It is a perspective view which shows typically the state which winds and produces an electrode body. It is a side view showing typically a vehicle (automobile) provided with a lithium secondary battery concerning one embodiment. 2 is a SEM image of a complex oxide according to Example 1. It is a SEM image of complex oxide concerning a comparative example. 4 is a graph showing charge / discharge characteristics of a lithium secondary battery constructed using the composite oxide according to Example 1. FIG. It is a graph which shows the charging / discharging characteristic of the lithium secondary battery constructed | assembled using the complex oxide which concerns on a comparative example. It is a graph which compares the diffraction pattern by the XRD measurement of the complex oxide (Example 2) obtained by omitting a temperature holding process, and the complex oxide (Example 3) obtained through the temperature holding process. Charging / discharging characteristics of a lithium secondary battery constructed using the composite oxide obtained by omitting the temperature holding process (Example 2) and the composite oxide obtained through the temperature holding process (Example 3), respectively. It is a graph which shows.

  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.

  The electrode active material provided by the present invention is an electrode active material for lithium secondary batteries (typically a positive electrode active material) made of a complex oxide having an amorphous structure, and lithium and at least one transition metal The composite oxide includes an element and at least one element capable of forming glass in the form of an oxide together with oxygen. Hereinafter, although the said electrode active material and the manufacturing method of this active material are demonstrated in detail, it is not intending to limit this invention to this embodiment.

  First, an electrode active material (typically a positive electrode active material) for a lithium secondary battery according to the present embodiment will be described. The electrode active material disclosed here is composed of a complex oxide having an amorphous structure (amorphous structure). The composite oxide having an amorphous structure according to the present invention is an amorphous type having no specific crystal structure such as a layered structure or a spinel structure. A composite oxide having a crystal structure such as a layered structure or a spinel structure has excellent battery characteristics (for example, cycle characteristics, high rate) as the lithium secondary battery using the oxide as an electrode active material has higher crystallinity and finer grains. Characteristic). Based on this principle, the complex oxide having an amorphous structure has a structure contrary to the complex oxide having the specific crystal structure, and is not suitable as an electrode active material for a lithium secondary battery in improving battery characteristics. Seems to be. However, since complex oxides with an amorphous structure are amorphous, the insertion positions of lithium ions are irregular and there are no restrictions on the crystal structure, so there is a possibility that a large amount of lithium ions can be occluded. doing. Therefore, it is expected as an electrode active material that can realize high capacity or high energy density.

Next, a method for producing an electrode active material (typically a positive electrode active material) for a lithium secondary battery made of a complex oxide having an amorphous structure according to this embodiment will be described.
The manufacturing method disclosed herein includes lithium, at least one transition metal element, and lithium composed of a complex oxide having an amorphous structure including oxygen and at least one element capable of forming a glass in an oxide form. This is a method for producing a method for producing an electrode active material for a secondary battery. In general, the production method includes a step of preparing a raw material mixture by dissolving a starting raw material for constituting the composite oxide in an organic solvent, a step of volatilizing an organic solvent obtained by heating the raw material mixture, and Firing. Details will be described below.

<Starting material>
First, a starting material for preparing a composite oxide having an amorphous structure including lithium, at least one transition metal element, and at least one element capable of forming glass in the form of an oxide together with oxygen is prepared. . As the starting material, at least a lithium source, the transition metal element source, and the glass-forming element source are prepared. As a supply source of each element, one type of compound may be used, or two or more types may be mixed and used. Moreover, the raw material compound which functions as a supply source of 2 or more types of elements can be used. For example, when a nickel source is required as the transition metal element source and a phosphorus source is required as the glass-forming element source, nickel phosphate hydrate or the like can be used.

The compound including a lithium source that is one of the above starting materials is not particularly limited as long as it can be dissolved in a solvent (here, an organic solvent) (some of which may be dispersed). Lithium compounds can be used. For example, lithium hydroxide, lithium carbonate, lithium sulfate, lithium nitrate, lithium peroxide, lithium phosphate, lithium oxalate, lithium acetate, or lithium iodide may be used. Particularly preferred examples include hydrates such as lithium acetate dihydrate [Li (CH ₃ COO) · 2H ₂ O].

The transition metal element source is not particularly limited but is preferably selected from the group consisting of manganese (Mn), nickel (Ni), cobalt (Co) and iron (Fe). A compound including a seed or two or more kinds of transition metal elements is exemplified. Particularly preferred are compounds including Mn.
The compound including such a transition metal element can be dissolved in a solvent (here, an organic solvent) (partly may be dispersed), various transition metal element hydroxides, oxides, various salts ( For example, compounds such as carbonate) and halides (eg fluoride) can be selected.

For example, examples of the compound containing the manganese source include mainly divalent or tetravalent manganese acetate, manganese oxalate, manganese carbonate, manganese oxide, manganese sulfate, manganese nitrate, manganese hydroxide, manganese oxyhydroxide, and the like. Manganese compounds can be used. Particularly preferable examples include manganese acetate (II) tetrahydrate [Mn (CH ₃ COO) ₂ .4H ₂ O] or manganese sulfate.
Examples of the compound containing the nickel source include mainly divalent or trivalent nickel acetate, nickel oxalate, nickel carbonate, nickel oxide, nickel sulfate, nickel nitrate, nickel hydroxide, nickel oxyhydroxide and the like. Nickel compounds can be used. A particularly preferable example is nickel acetate (II) tetrahydrate [Ni (CH ₃ COO) ₂ .4H ₂ O].
Furthermore, as the compound containing the cobalt source, for example, cobalt acetate, cobalt oxalate, cobalt carbonate, cobalt oxide, cobalt sulfate, cobalt nitrate, cobalt hydroxide, cobalt oxyhydroxide and the like are mainly divalent or trivalent. A cobalt compound can be used. A particularly preferred example is cobalt (II) acetate tetrahydrate [Co (CH ₃ COO) ₂ .4H ₂ O].
Furthermore, examples of the compound containing the iron source include mainly iron compounds such as divalent or trivalent iron chloride, iron oxide, iron oxalate, iron carbonate, iron oxide, iron sulfate, iron nitrate, and iron hydroxide. Any of these can be suitably used.

  Here, as the transition metal element source, one or more transition metal elements selected from the group consisting of manganese (Mn), nickel (Ni), cobalt (Co), and iron (Fe) are used. In addition, at least one metal element (that is, a transition metal element other than the main constituent metal element and / or a typical metal element) may be contained in a proportion preferably smaller than the molar ratio of the constituent metal elements. Examples of such metal elements include chromium (Cr), vanadium (V), magnesium (Mg), titanium (Ti), zirconium (Zr), niobium (Nb), molybdenum (Mo), tungsten (W), copper ( Cu, zinc (Zn), indium (In), tin (Sn), lanthanum (La), cerium (Ce), and the like.

The glass-forming element source includes at least one element capable of forming glass in the form of an oxide with oxygen, such as boron (B), aluminum (Al), silicon (Si), phosphorus (P), It is preferable to use an element source that supplies elements such as germanium (Ge), tellurium (Te), gallium (Ga), and bismuth (Bi). The elements listed above are in the form of oxides (glass-forming oxides) together with oxygen in B ₂ O ₃ , Al ₂ O ₃ , SiO ₂ , P ₂ O ₅ , GeO ₂ , TeO ₂ , Ga ₂ O ₃ , Bi _2. May be present at O ₃ . Such a glass-forming element source is a compound that includes the above-mentioned elements and is not particularly limited as long as it is a compound that can be dissolved (partly dispersed) in a solvent (here, an organic solvent). Can be done. Preferable specific examples include compounds including one or more elements selected from the group consisting of boron (B), phosphorus (P), and silicon (Si).

For example, the compound including a phosphorus source is not particularly limited as long as it is a compound that can be dissolved (partly dispersed) in a solvent (here, an organic solvent), and various phosphorus compounds may be used. it can. For example, ammonium hydrogen phosphate such as phosphoric acid, ammonium dihydrogen phosphate [NH ₄ H ₂ PO ₄ ] or diammonium hydrogen phosphate can be used. Alternatively, a solution containing phosphoric acid may be used as the phosphoric acid source. Preferably, phosphoric acid is used.
In addition, the compound including the boron source is not particularly limited as long as it is a compound that can be dissolved (partly dispersed) in a solvent (here, an organic solvent), and various boron compounds may be used. it can. For example, boric acid and boron oxide (B ₂ O ₃ ) are preferable.

<Preparation of raw material mixture>
Next, each of the prepared starting materials is weighed and dissolved in an organic solvent to prepare a raw material mixture. Such a raw material mixture has the general formula:
Li _a MX _b O _c (1)
(A, b and c in the formula (1) are
0 <a ≦ 2.5,
0 <b ≦ 3,
c = {a + (valence of M) + b × (valence of X)} / 2
Is a number that satisfies all
M is at least one transition metal element, and X is at least one element capable of forming glass in the form of an oxide with oxygen. )
It is more preferable to adjust (weigh) the amount of each starting material so that a composite oxide represented by
Here, the composite oxide obtained by the manufacturing method according to the present embodiment has an amorphous structure and can store a large amount of lithium ions because there is no restriction on the crystal structure. Therefore, the lithium supply source is prepared so that a in the formula (1) satisfies 0 <a ≦ 2.5 so that an excessive amount of lithium is contained, and the starting materials are mixed. Thereby, the electrode active material for lithium secondary batteries which consists of complex oxide which has an amorphous structure which can implement | achieve high capacity | capacitance and high energy density is compoundable.

Further, the M element in the above formula (1) is not particularly limited as long as it is at least one transition metal element. For example, at least one element selected from the group consisting of manganese (Mn), nickel (Ni), cobalt (Co) and iron (Fe) is more preferable. A high-capacity lithium secondary battery that can occlude more charge carriers (lithium) can be provided. Furthermore, by adjusting the mixing ratio of the transition element source so that the molar ratio of manganese after lithium becomes higher, the amount of costly transition metal materials such as cobalt and nickel can be reduced.
The X element in the formula (1) is not particularly limited as long as it is at least one element that can form glass in the form of an oxide together with oxygen. For example, by preparing a raw material mixture so as to include at least one element selected from the group consisting of boron (B), phosphorus (P), and silicon (Si), a specific crystal structure is obtained. A composite oxide having no amorphous structure can be obtained more suitably.

  The organic solvent for dissolving the starting material used here is not particularly limited as long as the starting material can be suitably dissolved. For example, chloroform, dichloromethane, dichloroethane, benzene, toluene, xylene, acetone, methyl ethyl ketone, tetrahydrofuran, dioxane, ethyl acetate, acetonitrile, dimethyl sulfoxide (DMSO), N, N-dimethylformamide (DMF), N, N-dimethylacetamide, Preferred examples include N-methyl-2-pyrrolidone (NMP), methyl ethyl ketone and the like. Of these, DMF can be particularly preferably used. In addition, such an organic solvent may be used individually by 1 type, or may mix and use 2 or more types. Moreover, you may use the mixed solvent which has the said organic solvent as a main component containing water (or lower alcohol, lower ketone, etc. which can be mixed with water uniformly).

  After adjusting the mixing mass ratio of each starting material, the starting material mixture is prepared by adding each starting material to the organic solvent and mixing and dissolving it sufficiently. In 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 is uniformly mixed and stably mixed. A raw material mixture in a state can be prepared.

<Volatilization of organic solvents>
Next, the process of volatilizing the organic solvent will be described. In this step, the prepared raw material mixture is heated to volatilize the organic solvent contained in the raw material mixture (typically, the raw material mixture is dried). By heating the raw material mixture before the firing step to be described later, the organic solvent (or a part) is volatilized from the raw material mixture and can be dried to a suitable state while suppressing crystal growth.

The heating temperature is not particularly limited as long as it is a temperature at which the organic solvent volatilizes (the boiling point of the organic solvent to be used or a temperature in the vicinity thereof, for example, a boiling point ± 20 ° C.), but a temperature exceeding at least 100 ° C. And it is preferable to heat a raw material mixture at the temperature lower than the maximum baking temperature in the baking process mentioned later. For example, it can be heated at a temperature of about 110 ° C to 400 ° C, preferably 120 ° C to 300 ° C, more preferably 130 ° C to 200 ° C, particularly preferably 140 ° C to 170 ° C, and preferably about 150 ° C. Thereby, the organic solvent can be effectively volatilized.
In addition, the heating time can adjust suitably holding time, confirming the dry state of a raw material mixture. For example, 12 hours or less, typically 5 hours or less, preferably 1 to 5 hours, and approximately 2 to 3 hours are preferable.
Moreover, as a heating method, it can heat favorably using suitable heating (drying) means, such as a hot air, vacuum, infrared rays, and far infrared rays. The atmosphere at the time of heating can be maintained in an air atmosphere, in an inert gas atmosphere such as nitrogen gas, or in an airtight container as needed depending on the type of solvent and starting material used.

<Temperature retention>
Next, after completion of the volatilization step, before the firing step described later, the raw material mixture from which the organic solvent has been volatilized is held at a temperature of 100 ° C. or lower (typically, the temperature of the heated raw material mixture is once reduced to 100 ° C. or lower). It is more preferable to perform a process of lowering the temperature until After the organic solvent is volatilized from the raw material mixture, when the temperature of the raw material mixture is set to 100 ° C. or lower, moisture is obtained and a gel is formed. Thus, it is possible from the composite oxide obtained by the production method to reduce the content of Li ₃ PO ₄ that does not contribute to charging and discharging. As a result, it is possible to provide an electrode active material (typically a positive electrode active material) for a lithium secondary battery capable of constructing a lithium secondary battery having a higher battery capacity or a higher energy density.
The holding temperature is not limited as long as it is 100 ° C. or lower, but for example, a temperature range from room temperature to 100 ° C. (typically 10 ° C. to 90 ° C., preferably 15 ° C. to 50 ° C., more preferably 20 ° C. By holding the raw material mixture at (C-30C), it can be changed to a gel state. In addition, the holding time is not particularly limited, but the raw material mixture may be held in the above temperature range, for example, all day, preferably 2 days or longer, preferably about 1 week.

<Baking>
Next, firing will be described. The raw material mixture after the organic solvent is volatilized (when the holding step is performed, after completion of the step) is fired. The firing is desirably performed in an oxidizing atmosphere, for example, the air or an atmosphere richer in oxygen than the air. Also, the firing temperature is higher than the temperature heated in the organic solvent volatilization step and rises to the maximum firing temperature set in the temperature range of 400 ° C. or lower (referring to the firing temperature set in a device such as a heating furnace). Bake warm. Typically, firing can be performed at a maximum firing temperature of about 200 ° C to 400 ° C, preferably 250 ° C to 380 ° C, and preferably about 300 ° C to 350 ° C. Since firing is possible at such a lower maximum firing temperature, a composite oxide having a target amorphous structure can be obtained more efficiently. The fired product obtained after the firing step has an amorphous primary particle whose average particle size based on observation with a scanning electron microscope is typically 1 μm or less (for example, about 100 nm to 500 nm, preferably about 200 to 300 nm). It is composed of secondary particles formed by aggregating a complex oxide having a structure.

<Crushing>
Moreover, it is preferable to grind the fired product (secondary particles) after firing the raw material mixture. By pulverizing, granulating and classifying by an appropriate means (for example, a ball mill, a mixer, etc.), a composite oxide having an amorphous structure substantially constituted by primary particles having a large specific surface area can be obtained. In a conventional production method such as a melt quenching method, a composite oxide having an amorphous structure with a small average particle diameter cannot be obtained even if the fired product is pulverized. However, according to the production method of the present invention, it is possible to produce a composite oxide having an amorphous structure having a smaller average particle diameter (larger specific surface area) by firing in a low temperature range. Thereby, the electrode active material for lithium secondary batteries which can implement | achieve high capacity | capacitance or high energy density can be provided.
In addition, powdered carbon materials (various carbon blacks such as acetylene black, furnace black, ketjen black, or graphite) that can be further used as a conductive material are added to the pulverized fired product (a composite oxide having an amorphous structure). By adding and grinding (mixing) together, the surface of the composite oxide can be coated with a carbon material. Thereby, the electroconductivity of the electrode active material which consists of this complex oxide can be improved.

Hereinafter, a positive electrode in which a composite oxide having an amorphous structure obtained by the production method disclosed herein is used as an electrode active material for a lithium secondary battery, and an embodiment of a lithium secondary battery including the positive electrode, Although a square-shaped lithium secondary battery including a revolving electrode body will be described, the present invention is not intended to be limited to such an example.
Further, matters other than the matters specifically mentioned in the present specification and matters necessary for the implementation of the present invention (for example, the configuration and manufacturing method of an electrode body, a general configuration related to construction of a lithium secondary battery and other batteries) Technology, etc.) can be understood as a design matter of those skilled in the art based on the prior art in the field. 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 relationships (length, width, thickness, etc.) in each drawing do not reflect actual dimensional relationships.

FIG. 1 is a perspective view schematically showing a rectangular lithium secondary battery according to an embodiment, and FIG. 2 is a cross-sectional view taken along line II-II in FIG. FIG. 3 is a perspective view schematically showing a state in which the electrode body is wound and manufactured.
As shown in FIGS. 1 and 2, the lithium secondary battery 100 according to the present embodiment includes a rectangular parallelepiped battery case 10 and a lid body 14 that closes the opening 12 of the case 10. A flat electrode body (wound electrode body 20) and an electrolyte can be accommodated in the battery case 10 through the opening 12. The lid 14 is provided with a positive terminal 38 and a negative terminal 48 for external connection, and a part of the terminals 38 and 48 protrudes to the surface side of the lid 14. Also, some of the external terminals 38 and 48 are connected to the internal positive terminal 37 or the internal negative terminal 47, respectively, inside the case.

  Next, the wound electrode body 20 according to the present embodiment will be described with reference to FIGS. 2 and 3. As shown in FIG. 2, the wound electrode body 20 includes a sheet-like positive electrode sheet 30 having a positive electrode active material layer 34 on the surface of a long positive electrode current collector 32, a long sheet-like separator 50, a long A sheet-like negative electrode sheet 40 having a negative electrode active material layer 44 on the surface of a long negative electrode current collector 42 is formed. As shown in FIG. 3, in the cross-sectional view in the winding axis direction R, the positive electrode sheet 30 and the negative electrode sheet 40 are stacked via two separators 50. 50, the negative electrode sheet 40, and the separator 50 are laminated in this order. The laminate is wound around a shaft core (not shown) in a cylindrical shape, and is formed into a flat shape by squashing the obtained wound electrode body 20 from the side surface direction.

As shown in FIG. 3, the wound electrode body 20 according to the present embodiment has a positive electrode active material layer formed on the surface of the positive electrode current collector 32 at the center in the winding axis direction R. 34 and the negative electrode active material layer 44 formed on the surface of the negative electrode current collector 42 overlap each other to form a densely stacked portion. Further, in a cross-sectional view in the direction along the winding axis direction R, the exposed portion of the positive electrode current collector 32 (positive electrode active material layer) without forming the positive electrode active material layer 34 at one end in the direction R. The non-forming portion 36) is laminated in a state of protruding from the separator 50 and the negative electrode sheet 40 (or a dense laminated portion of the positive electrode active material layer 34 and the negative electrode active material layer 44). That is, a positive electrode current collector laminated portion 35 formed by laminating the positive electrode active material layer non-forming portion 36 in the positive electrode current collector 32 is formed at the end of the electrode body 20. Also, the other end of the electrode body 20 has the same configuration as that of the positive electrode sheet 30, and the negative electrode active material layer non-formation portion 46 in the negative electrode current collector 42 is laminated to form the negative electrode current collector lamination portion 45. ing.
Here, as the separator 50, a separator having a width larger than the width of the laminated portion of the positive electrode active material layer 34 and the negative electrode active material layer 44 and smaller than the width of the electrode body 20 is used, and the positive electrode current collector 32 and the negative electrode The current collectors 42 are disposed so as to be sandwiched between the stacked portions of the positive electrode active material layer 34 and the negative electrode active material layer 44 so as not to contact each other and cause an internal short circuit.

  The positive electrode (typically, positive electrode sheet 30) of the lithium secondary battery according to the present embodiment has a configuration in which a positive electrode active material layer 34 containing a positive electrode active material is formed on a long positive electrode current collector 32. Prepare. As the positive electrode current collector 32, a conductive member made of a highly conductive metal is preferably used. For example, aluminum or an alloy containing aluminum as a main component can be used. The shape of the positive electrode current collector 32 may vary depending on the shape of the lithium secondary battery, and is not particularly limited, and may be various forms such as a rod shape, a plate shape, a sheet shape, a foil shape, and a mesh shape. As the positive electrode active material, an electrode active material made of a complex oxide having an amorphous structure obtained by using the manufacturing method disclosed herein is used.

  In addition to the above-described positive electrode active material, the positive electrode active material layer 34 may contain one or more kinds of conductive materials and binders that can be blended in a general lithium secondary battery as necessary. it can. As such a conductive material, a conductive powder material such as carbon powder or carbon fiber is preferably used. As the carbon powder, various carbon blacks such as acetylene black, furnace black, ketjen black, and graphite powder are preferable. In addition, conductive fibers such as carbon fibers and metal fibers, metal powders such as copper and nickel, and organic conductive materials such as polyphenylene derivatives can be contained alone or as a mixture thereof. In addition, only 1 type may be used among these, or 2 or more types may be used together.

  Moreover, as the binder, the same binder as that used for the positive electrode of a general lithium secondary battery can be appropriately employed. For example, it is preferable to select a polymer that is soluble or dispersible in the solvent used. When an aqueous solvent is used, cellulose polymers such as carboxymethylcellulose (CMC) and hydroxypropylmethylcellulose (HPMC); polyvinyl alcohol (PVA); polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer Water-soluble or water-dispersible polymers such as fluorine resins such as (FEP); vinyl acetate copolymers; rubbers such as styrene butadiene rubber (SBR) and acrylic acid-modified SBR resins (SBR latex); be able to. When a non-aqueous solvent is used, a polymer such as polyvinylidene fluoride (PVDF) or polyvinylidene chloride (PVDC) can be preferably used. Such a binder may be used individually by 1 type, and may be used in combination of 2 or more type. In addition to the function as a binder, the polymer material exemplified above may be used for the purpose of exhibiting the function as a thickener or other additive of the above composition.

Next, a method for producing the positive electrode of the lithium secondary battery according to this embodiment will be described.
First, a positive electrode active material (a composite oxide having an amorphous structure obtained by using the manufacturing method disclosed herein), a conductive material, a binder, and the like are mixed with an appropriate solvent (aqueous solvent or non-aqueous solvent). Then, a paste or slurry-like composition for forming a positive electrode active material layer (hereinafter referred to as “positive electrode active material layer forming paste”) is prepared. As for the blending ratio of each constituent material, for example, the ratio of the positive electrode active material in the positive electrode active material layer is preferably about 50% by mass or more (typically 50 to 95% by mass), and about 70 to 95% by mass. % (For example, 75 to 90% by mass) is more preferable. The proportion of the conductive material in the positive electrode active material layer can be, for example, about 2 to 25% by mass, and preferably about 2 to 20% by mass. Furthermore, in the composition using the binder, the proportion of the binder in the positive electrode active material layer can be, for example, about 1 to 10% by mass, and usually about 2 to 5% by mass. The paste prepared by mixing the constituent materials in this way is applied to the positive electrode current collector 32, and after the solvent is evaporated and dried, the paste is compressed (pressed). Thereby, the positive electrode of the lithium secondary battery in which the positive electrode active material layer is formed on the positive electrode current collector is obtained.

  As a solvent used for preparing the positive electrode active material layer forming paste, either an aqueous solvent or a non-aqueous solvent can be used. The aqueous solvent is typically water, but may be any water-based solvent as a whole, that is, water or a mixed solvent mainly composed of water can be preferably used. As the solvent other than water constituting the mixed solvent, one or more organic solvents (lower alcohol, lower ketone, etc.) that can be uniformly mixed with water can be appropriately selected and used. For example, it is preferable to use a solvent in which about 80% by mass or more (more preferably about 90% by mass or more, more preferably about 95% by mass or more) of the aqueous solvent is water. A particularly preferred example is a solvent consisting essentially of water. Further, preferred examples of the non-aqueous solvent include N-methyl-2-pyrrolidone (NMP), methyl ethyl ketone, toluene and the like.

  In addition, as a method of apply | coating the said paste to a positive electrode electrical power collector, the technique similar to a conventionally well-known method can be employ | adopted suitably. For example, the paste can be suitably applied to the positive electrode current collector by using an appropriate application device such as a slit coater, a die coater, a gravure coater, or a comma coater. Moreover, when drying a solvent, it can dry favorably by using natural drying, a hot air, low-humidity air, a vacuum, infrared rays, far-infrared rays, and an electron beam individually or in combination. Furthermore, as a 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, 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.

  Next, the negative electrode of the lithium secondary battery according to this embodiment will be described. The negative electrode (typically, the negative electrode sheet 40) may have a configuration in which a negative electrode active material layer 44 is formed on a long negative electrode current collector 42 (for example, a copper foil). As the negative electrode current collector serving as the base material of the negative electrode, a conductive member made of a highly conductive metal is preferably used. For example, copper or an alloy containing copper as a main component can be used. The shape of the negative electrode current collector may vary depending on the shape of the lithium secondary battery and the like, and thus is not particularly limited, and may be various forms such as a rod shape, a plate shape, a sheet shape, a foil shape, and a mesh shape.

  The negative electrode active material layer formed on the surface of the negative electrode current collector contains a negative electrode active material capable of inserting and extracting lithium ions serving as charge carriers. As the negative electrode active material, one or more materials conventionally used in lithium secondary batteries can be used without particular limitation. An example is carbon particles. A particulate carbon material (carbon particles) containing a graphite structure (layered structure) at least partially is preferably used. Any carbon material of a so-called graphitic material (graphite), non-graphitizable carbon material (hard carbon), easily graphitized carbon material (soft carbon), or a combination of these materials is preferably used. obtain. Among these, graphite particles can be preferably used. Graphite particles (eg, graphite) are excellent in conductivity because they can suitably occlude lithium ions as charge carriers. Further, since the particle size is small and the surface area per unit volume is large, it can be a negative electrode active material more suitable for high power charge / discharge.

  In addition to the negative electrode active material, the negative electrode active material layer may contain an optional component such as a binder as necessary. As such a binder, the same binder as that used for the negative electrode of a general lithium secondary battery can be adopted as appropriate, and functions as the binder listed in the components of the positive electrode described above. The various polymer materials obtained can be suitably used.

  Next, a method for producing a negative electrode for a lithium secondary battery according to this embodiment will be described. In order to form a negative electrode active material layer on the surface of the negative electrode current collector, first, the negative electrode active material is mixed with the appropriate solvent (aqueous solvent or non-aqueous solvent) together with a binder or the like to form a paste or slurry. The negative electrode active material layer forming composition (hereinafter referred to as “negative electrode active material layer forming paste”) is prepared. As for the blending ratio of each constituent material, for example, the ratio of the negative electrode active material in the negative electrode active material layer is preferably about 50% by mass or more, and is about 85 to 99% by mass (for example, 90 to 97% by mass). It is more preferable. Further, the ratio of the binder in the negative electrode active material layer can be, for example, about 1 to 15% by mass, and is usually preferably about 3 to 10% by mass. The paste thus prepared is applied to the negative electrode current collector, the solvent is volatilized and dried, and then compressed (pressed). Thereby, the negative electrode of the lithium secondary battery which has the negative electrode active material layer formed using this paste on a negative electrode collector is obtained. In addition, the application | coating, drying, and the compression method can use a conventionally well-known means similarly to the manufacturing method of the above-mentioned positive electrode.

  A rough procedure for constructing the lithium secondary battery 100 according to an embodiment will be described using the positive electrode sheet and the negative electrode sheet thus manufactured. The prepared positive electrode sheet 30 and negative electrode sheet 40 are stacked and wound together with two separators 50, and are crushed and crushed from the stacking direction to form the electrode body 20 into a flat shape and accommodate in the battery case 10. After injecting the electrolyte, the lid 14 is attached to the case opening 12 and sealed, whereby the lithium secondary battery 100 of this embodiment can be constructed. There is no particular limitation on the structure, size, material (for example, metal or laminate film) of the battery case 10 and the like.

  Moreover, as a suitable separator sheet 50 used between the positive / negative electrode sheets 30 and 40, what was comprised with porous polyolefin resin is mentioned. For example, a porous separator sheet made of synthetic resin (for example, made of polyolefin such as polyethylene) can be suitably used. When a solid electrolyte or a gel electrolyte is used as the electrolyte, there may be a case where a separator is unnecessary (that is, in this case, the electrolyte itself can function as a separator).

Moreover, the electrolyte can use the thing similar to the nonaqueous electrolyte conventionally used for a lithium secondary battery without limitation. Such a nonaqueous electrolytic solution typically has a composition in which a supporting salt is contained in a suitable nonaqueous solvent. The non-aqueous solvent is selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), N, N-dimethylformamide (DMF), ethyl methyl carbonate (EMC), and the like. 1 type or 2 types or more can be used. Examples of the supporting salt include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ). _3. Lithium compounds (lithium salts) such as LiI can be used. In addition, the density | concentration of the support salt in a nonaqueous electrolyte solution may be the same as that of the nonaqueous electrolyte solution used with the conventional lithium secondary battery, and there is no restriction | limiting in particular. An electrolyte containing an appropriate lithium compound (supporting salt) at a concentration of about 0.1 to 5 mol / L can be used.

  As described above, the lithium secondary battery 100 constructed in this way has a high battery capacity or a high energy density. Therefore, the lithium secondary battery 100 is particularly preferably used as a power source for a motor (electric motor) mounted on a vehicle such as an automobile. obtain. Therefore, as schematically shown in FIG. 4, the present invention provides a vehicle 1 (typically an automobile, in particular a hybrid) provided with such a lithium secondary battery (typically, a plurality of series-connected batteries) 100 as a power source. Automobiles, electric vehicles, automobiles equipped with electric motors such as fuel cell vehicles).

  In the following test examples, a lithium secondary battery (in this case, a positive electrode active material) using an electrode active material for a lithium secondary battery made of a composite oxide having an amorphous structure obtained by the production method disclosed herein (a positive electrode active material) A sample battery was constructed and its performance was evaluated.

<Example 1: Synthesis of positive electrode active material>
In the following procedure, to prepare a positive active material (Example 1) for a lithium secondary battery comprising a composite oxide having an amorphous structure _{(Li 2 MnP 0.5 B 1.5 O} 5.5).
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. 4H ₂ O], phosphoric acid (H ₃ PO ₄ ) as a phosphorus source, and boric acid (H ₃ BO ₃ ) as a boron source, a starting material for forming a composite oxide having the above composition ratio Raw materials were prepared. The starting material was added to an organic solvent (DMF), dissolved, and stirred for 3 hours to prepare a starting material mixture. Subsequently, the raw material mixture was heated (dried) at 150 ° C. for 2 hours to volatilize DMF. When the organic solvent volatilized, the temperature was raised to 350 ° C. (maximum firing temperature) without lowering the temperature. The composite oxide having an amorphous structure according to Example 1 was obtained by baking as it was for 5 hours. The obtained composite oxide was pulverized (stirred) at 300 rpm for 3 hours using a ball mill, and observed with a scanning electron microscope (SEM). FIG. 5 is a composite oxide according to Example 1 taken by SEM.

<Comparative example: Synthesis of positive electrode active material>
A positive electrode active material (test example) for a lithium secondary battery made of a composite oxide having an amorphous structure (Li ₂ MnP _0.5 B _1.5 O _5.5 ) was synthesized by the following procedure. That is, lithium hydroxide (LiOH) as a lithium source, manganese (II) oxide (MnO) as a manganese source, diphosphorus pentoxide (P ₂ O ₅ ) as a phosphorus source, and boron oxide as a boron source A starting material for constituting a composite oxide having the above composition ratio including (B ₂ O ₃ ) was prepared. The starting materials were mixed to prepare a starting material mixture, heated to a temperature range of 1000 to 1200 ° C., and heated until the mixture melted. Thereafter, the molten raw material mixture was poured into ice water and rapidly cooled to obtain a composite oxide having an amorphous structure according to a comparative example. The obtained composite oxide was pulverized (stirred) at 300 rpm for 3 hours using a ball mill, and observed with a scanning electron microscope (SEM). FIG. 6 is a composite oxide according to a comparative example taken by SEM.

  The particle diameters of the composite oxide having the amorphous structure according to Example 1 (FIG. 5) and the composite oxide having the amorphous structure according to the comparative example (FIG. 6) are compared. From the SEM image shown in FIG. 5, the average particle size of the composite oxide according to Example 1 was approximately 200 nm to 300 nm. On the other hand, from the SEM image shown in FIG. 6, the average particle size of the composite oxide according to the comparative example was about 2 μm to 3 μm. From this, it was confirmed that the composite oxide according to Example 1 had a smaller average particle diameter based on observation with a scanning electron microscope.

Next, the positive electrode of the lithium secondary battery for a test was produced.
First, the composite oxide having an amorphous structure as the synthesized positive electrode active material and acetylene black as the conductive material are added so that the mass% ratio of these materials is 70:25, and the ball mill is prepared. And mixed at 300 rpm. The positive electrode active material according to the example having a smaller average particle diameter was mixed for 24 hours after adding the conductive material. On the other hand, the positive electrode active material according to the comparative example was mixed for 3 hours after adding the conductive material.
Next, when forming the positive electrode active material layer in the positive electrode, a positive electrode active material layer forming paste was prepared. A composite oxide having an amorphous structure as a positive electrode active material, acetylene black as a conductive material, and polytetrafluoroethylene (PTFE) as a binder have a mass% ratio of these materials of 70: 25: 5 The binder was weighed so that ion-exchanged water was added and mixed to prepare 0.143 g of a positive electrode active material layer forming paste.
And the said paste was apply | coated to the aluminum foil as a positive electrode electrical power collector, and the water | moisture content in this paste was dried (evaporated). Furthermore, it was stretched into a sheet shape with a roller press, and an active material layer was formed on the surface of the positive electrode current collector. And it punched circularly with the punch of diameter 15mm, and prepared the positive electrode.

  Next, a negative electrode for a lithium secondary battery for testing was prepared. A lithium metal foil was prepared and punched out with a punch having a diameter of 15 mm to prepare a negative electrode.

A 2032 type (diameter 20 mm, thickness 3.2 mm) coin-type test lithium secondary battery was constructed using the positive electrode and negative electrode prepared above. That is, a circular positive electrode and a separator impregnated with a non-aqueous electrolyte are laminated and arranged inside an outer can that forms the outer casing on the positive electrode side, and after pressing the periphery of the separator with a gasket, A negative electrode, a spacer for adjusting the thickness, and a leaf spring were sequentially arranged on the separator. Then, the inside of the accommodated outer can was closed with an outer lid, and the outer can and the peripheral edge of the outer lid were sealed to construct a lithium secondary battery for testing.
In addition, as a non-aqueous electrolyte, 1 mol / L LiPF6 was dissolved in a 1: 1: 3 (volume ratio) mixed solvent of propylene carbonate (PC), ethylene carbonate (EC), and dimethyl carbonate (DMC). Was used. Moreover, as a separator, the three-layer film (PE / PP / PE film) made from polyethylene / polypropylene / polyethylene was used.

[Charge / discharge characteristics test]
The following charge / discharge characteristic tests were performed on the lithium secondary batteries constructed using the composite oxide having the amorphous structure according to Example 1 and the comparative example constructed as described above as the positive electrode active material.
The test conditions for the charge / discharge characteristics were as follows. At a measurement temperature of 25 ° C., the battery was charged to 5.0 V with a constant current of a current density of 0.1 mA / cm ² , 10 minutes later, and then discharged to 2.2 V with the same current density. The measurement results of the specific capacity are shown in FIGS.

FIG. 7 is a graph showing charge / discharge characteristics of a lithium secondary battery constructed using the composite oxide according to Example 1 as a positive electrode active material, and FIG. 8 shows the composite oxide according to the comparative example as a positive electrode active material. It is a graph which shows the charging / discharging characteristic of the lithium secondary battery constructed | assembled using as. 7 and 8, the horizontal axis represents the specific capacity, and the vertical axis represents the lithium reference electrode potential.
As is clear from FIG. 7 and FIG. 8, it was shown that the lithium secondary battery constructed using the composite oxide according to Example 1 has a larger specific capacity during charge / discharge. Compared with the specific capacity at the time of discharge (2.2 V), the specific capacity of the lithium secondary battery constructed using the composite oxide according to the comparative example shows about 30 mAh / g, whereas the composite capacity according to Example 1 The specific capacity of the lithium secondary battery constructed using the oxide was about 80 mAh / g.

<Example 2: Synthesis of positive electrode active material>
Furthermore, it was synthesized composite oxide having an amorphous structure positive electrode active material _{(Li 2 MnP 1 B 1 O} 6) made of a lithium secondary battery (Example 2). Among the procedures for synthesizing the positive electrode active material for the lithium secondary battery made of the composite oxide (Li ₂ MnP _0.5 B _1.5 O _5.5 ) having an amorphous structure according to Example 1, the firing temperature is 300. The compound was synthesized in the same procedure using the same starting materials as in Example 1 except that the temperature was changed to ° C.

<Example 3: Synthesis of positive electrode active material>
It was also synthesized composite oxide having an amorphous structure positive electrode active material _{(Li 2 MnP 1 B 1 O} 6) made of a lithium secondary battery (Example 3). Among the procedures for synthesizing the positive electrode active material for the lithium secondary battery made of the composite oxide (Li ₂ MnP _0.5 B _1.5 O _5.5 ) having an amorphous structure according to Example 1, the firing temperature is 300. The same starting materials as in Example 1 were used except that the temperature was changed to 0 ° C. and the temperature of the raw material mixture after the organic solvent was volatilized was temporarily lowered to 100 ° C. or lower (room temperature in this case). And synthesized in the same procedure.
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. 4H ₂ O], phosphoric acid (H ₃ PO ₄ ) as a phosphorus source, and boric acid (H ₃ BO ₃ ) as a boron source, a starting material for forming a composite oxide having the above composition ratio Raw materials were prepared. The starting material was added to an organic solvent (DMF), dissolved, and stirred for 3 hours to prepare a starting material mixture. Subsequently, the raw material mixture was heated (dried) at 150 ° C. for 2 hours to volatilize DMF. After the organic solvent volatilized, the temperature of the raw material mixture was kept at room temperature for 1 week in order to lower the temperature of the raw material mixture. After the temperature holding step, the raw material mixture was heated to 300 ° C. The composite oxide having an amorphous structure according to Example 3 was obtained by baking as it was for 5 hours. The obtained composite oxide was pulverized (stirred) at 300 rpm for 3 hours using a ball mill.

The composite oxides having an amorphous structure according to Example 2 and Example 3 synthesized above were subjected to XRD measurement, and the respective X-ray diffraction patterns were compared. FIG. 9 shows a comparison graph of X-ray diffraction patterns.
The X-ray diffraction pattern of the composite oxide (Example 3) obtained through the upper temperature holding step in FIG. 9 shows the X of the composite oxide (Example 2) obtained by omitting the lower temperature holding step. In the line diffraction pattern, no peak was observed at a position where the 2θ value was around 22 °. Li ₃ PO _4, which is a compound corresponding to such a peak, can be reduced from the composite oxide by performing a process of keeping the temperature at 100 ° C. or lower (here, room temperature) after volatilizing the organic solvent. Was confirmed.

  Using the composite oxides according to Example 2 and Example 3 synthesized above, a positive electrode was manufactured in the same procedure as the above-described positive electrode manufacturing method. Next, using the produced positive electrode, each test lithium secondary battery was prepared in the same procedure as the construction method of the above-described 2032 type (diameter 20 mm, thickness 3.2 mm) coin-type test lithium secondary battery. It was constructed.

[Charge / discharge characteristics test]
A charge / discharge characteristic test was performed on the lithium secondary battery constructed using the composite oxide according to Example 2 and Example 3 constructed as described above as the positive electrode active material under the same conditions as described above. FIG. 10 shows the measurement results of specific capacity.
As shown in FIG. 10, the lithium secondary battery constructed using the composite oxide obtained through the temperature holding process according to Example 3 is shown to greatly improve the specific capacity during charging and discharging. It was.

  As mentioned above, although this invention was demonstrated in detail, the said embodiment and Example are only illustrations and what changed and changed the above-mentioned specific example is contained in the invention disclosed here. For example, the battery of the various content from which an electrode body structural material and electrolyte differ may be sufficient. Further, the size and other configurations of the battery can be appropriately changed depending on the application (typically for in-vehicle use).

  Since the lithium secondary battery constructed using the electrode active material for a lithium secondary battery comprising a complex oxide having an amorphous structure obtained by the production method of the present invention is excellent in charge / discharge characteristics as described above, It can be suitably used as a power source for a motor (electric motor) mounted on a vehicle such as an automobile. Therefore, as schematically shown in FIG. 4, the present invention provides a vehicle 1 (typically an automobile, in particular a hybrid) provided with such a lithium secondary battery (typically, a plurality of series-connected batteries) 100 as a power source. Automobiles, electric vehicles, automobiles equipped with electric motors such as fuel cell vehicles).

DESCRIPTION OF SYMBOLS 1 Vehicle 10 Battery case 12 Opening part 14 Cover body 20 Winding electrode body 30 Positive electrode sheet 32 Positive electrode collector 34 Positive electrode active material layer 35 Positive electrode collector lamination | stacking part 36 Positive electrode active material layer non-formation part 37 Positive electrode current collection terminal 38 External positive electrode current collector terminal 40 Negative electrode sheet 42 Negative electrode current collector 44 Negative electrode active material layer 45 Negative electrode current collector laminated portion 46 Negative electrode active material layer non-formation portion 47 Negative electrode current collector terminal 48 External negative electrode current collector terminal 50 Separator 100 Lithium secondary Battery R Winding axis direction

Claims (12)

A complex oxide having an amorphous structure,
Method for producing an electrode active material for a lithium secondary battery comprising a composite oxide, comprising lithium, at least one transition metal element, and at least one element capable of forming glass in the form of an oxide together with oxygen And the following steps:
A step of preparing a raw material mixture by dissolving a starting raw material for constituting the composite oxide in an organic solvent, including at least a lithium source, the transition metal element source, and the glass-forming element source;
Heating the raw material mixture to volatilize the organic solvent; and baking the raw material mixture after volatilizing the organic solvent;
Manufacturing method.   The manufacturing method of Claim 1 including the process of hold | maintaining the raw material mixture after volatilizing the said organic solvent at the temperature of 100 degrees C or less after completion | finish of the said volatilization process.   The manufacturing method according to claim 1 or 2, wherein, in the volatilization step, the raw material mixture is heated at a temperature that is at least higher than 100 ° C and lower than a maximum baking temperature in the baking step.   The manufacturing method according to claim 3, wherein in the firing step, the maximum firing temperature is set to 400 ° C. or lower. The raw material mixture has the general formula:
Li _a MX _b O _c (1)
(A, b and c in the formula (1) are
0 <a ≦ 2.5,
0 <b ≦ 3,
c = {a + (valence of M) + b × (valence of X)} / 2
Is a number that satisfies all
M is at least one transition metal element, and X is at least one element capable of forming glass in the form of an oxide with oxygen. )
The manufacturing method in any one of Claims 1-4 prepared so that the complex oxide shown by this may be produced | generated.   The manufacturing method according to claim 5, wherein the M element is one or more elements selected from the group consisting of Mn, Ni, Co, and Fe.   The manufacturing method according to claim 5 or 6, wherein the X element is one or more elements selected from the group consisting of B, P and Si.   The manufacturing method in any one of Claims 1-7 using the hydrate of the compound containing the said element as said lithium source and / or said transition metal element source.   The manufacturing method in any one of Claims 1-8 which further includes the process of grind | pulverizing the baked product obtained after the said baking process. An electrode active material for Lithium secondary battery,
It is composed of a complex oxide having an amorphous structure,
The composite oxide includes lithium, at least one transition metal element, and at least one element capable of forming glass in the form of an oxide with oxygen,
An electrode active material, wherein an average particle diameter of primary particles based on observation with a scanning electron microscope is 1 μm or less.   A lithium secondary battery comprising a positive electrode using the electrode active material for a lithium secondary battery according to claim 10.   A vehicle comprising the lithium secondary battery according to claim 11.