JP2015145320A - Lithium-containing metal oxide for positive electrode of lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium-containing metal oxide suitable as a positive electrode active material of a lithium ion battery which has a high capacity and readily allows a large current to flow when discharging.SOLUTION: There is provided a lithium-containing metal oxide which has a crystal in which a lithium-containing metal oxide A having a spinel structure represented by the following composition formula (1): LiMnMO...(1){in the formula, M is one or more metal elements other than Mn and Li and satisfies the relations: 0≤k<1, 0<x≤0.5 and 0≤α<1} and a lithium-containing metal oxide B having a laminar structure in which Li is arrayed in layer represented by the following composition formula...(2): LiMnM'O(2){in the formula, M' is one or more metal elements other than Mn and Li and satisfies the relations: 0<y<1 and 0≤β<1} are solid-dissolved.

Description

  The present invention relates to a lithium-containing metal oxide suitable as a positive electrode active material of a lithium ion secondary battery, a production method thereof, a positive electrode using the same, and a secondary battery using the positive electrode.

  As interest in environmental technology has increased in recent years, there is an increasing expectation for storage devices for electrical energy generated by solar power generation and wind power generation and for battery applications in electric vehicles. In particular, lithium ion secondary batteries, which are representative of power storage devices, are required to have higher capacities in order to improve power storage capacity. Since the capacity of the lithium ion secondary battery is governed by the lithium content of the lithium-containing metal oxide at the positive electrode in the battery, it is possible to develop a lithium-containing metal oxide with a high lithium content. It is necessary for higher capacity.

As a lithium-containing metal oxide, a composition formula LiMeO ₂ {wherein Me is a transition metal element. } The actual capacity of a current lithium ion secondary battery using a layered lithium oxide crystal represented by the formula is about 160 mAh / g, and it is actually difficult to increase the capacity beyond this. In response to this problem, lithium-containing metal oxides have been reported that achieve a high capacity by increasing the lithium content in the lithium-containing metal oxide.
For example, the following Patent Document 1 discloses a lithium oxide crystal having the same layer structure as the layered lithium oxide crystal described by the above-described composition formula LiMeO ₂ , but the composition formula Li ₂ MnO ₃ having a higher lithium content. The composition formula ωLiMeO _2. (1-ω) Li ₂ MnO ₃ {where 0 <ω <1. } The lithium containing metal oxide represented by this is described.

In Patent Document 2 below, the composition formula LiMn _2−ε Me ′ _ε O ₄ {wherein Me ′ is a metal element other than Mn, and 0 ≦ ε ≦ 0.5. } The composition formula ωLi ₂ MnO _3. (1-ω) LiMn is a crystal in which a crystal having a spinel structure represented by the following formula and a layered lithium oxide crystal described by the composition formula Li ₂ MnO ₃ are dissolved. _2-ε Me ′ _ε O ₄ {where 0 <ω <1, Me ′ is a metal element other than Mn, and 0 ≦ ε ≦ 0.5. } The lithium containing metal oxide represented by this is described.

Furthermore, the following Patent Document 3 includes a lithium-containing metal oxide including a crystal in which three kinds of crystals composed of the above-described LiMeO ₂ , Li ₂ MnO ₃ , and LiMn _2−ε Me ′ _ε O ₄ are solid-solved. Things are listed.
These lithium-containing metal oxides in which a crystal represented by the composition formula Li ₂ MnO ₃ having a large amount of lithium is partially dissolved in the crystal constituting the lithium-containing metal oxide are represented by the composition formula LiMeO ₂ . The lithium content is higher than the current lithium-containing metal oxides represented, and a high capacity of about 200 mAh / g or more has been reported as the actual capacity of a lithium ion secondary battery using this as a positive electrode.

US Pat. No. 6,677,082 US Pat. No. 7,635,536 US Pat. No. 7,790,308

However, a lithium ion battery using a lithium-containing metal oxide composed of a crystal in which a crystal represented by the composition formula Li ₂ MnO ₃ is dissolved is generally large in electric resistance and difficult to pass a large current during discharge. At present, it has not been put into practical use. One reason is that the electrical resistance of the crystal represented by the composition formula Li ₂ MnO ₃ is large.
The reason why the electric resistance of the crystal represented by the composition formula Li ₂ MnO ₃ is large has not been completely clarified, but the tetravalent manganese constituting the crystal alone has a large band gap in the vicinity of the Fermi level. It is presumed to be physical. Therefore, although not bound by a specific theory, a part of the crystal manganese represented by the composition formula Li ₂ MnO ₃ is substituted with a different metal element, and the bonding mode of the metal element and oxygen associated with the substitution Changes the electronic state of the structure corresponding to Li ₂ MnO ₃ , the band gap in the vicinity of the Fermi level becomes smaller, the crystal changes like a conductor, and the electrical resistance decreases, resulting in a large current. It is expected to be easy to flow.
In view of such circumstances, the problem to be solved by the present invention is to provide a lithium-containing metal oxide as a positive electrode active material of a lithium ion secondary battery that has a high lithium content and that easily allows a large current to flow during discharge. Is to provide.

As a result of intensive investigations and repeated experiments to solve the above problems, the present inventor has found that lithium and a metal oxide A having a spinel structure containing at least one metal element other than manganese and manganese and lithium, and a composition formula Two types of crystals of lithium-containing metal oxide B having a layered structure in which a part of manganese in the crystal structure represented by Li ₂ MnO ₃ is substituted with at least one metal element other than manganese and lithium are in solid solution. The present inventors have found that a lithium ion secondary battery using a lithium-containing metal oxide can easily flow a large current during discharging, and has completed the present invention.

That is, the present invention is as follows.
[1] The following composition formula (1):
Li _{1 + k} Mn _2-x M _x O _4-α (1)
{In the formula, M is one or more metal elements other than Mn and Li, and satisfies the relationship of 0 ≦ k <1, 0 <x ≦ 0.5, and 0 ≦ α <1. } A lithium-containing metal oxide A having a spinel structure represented by the following formula (2):
Li ₂ Mn _1-y M ′ _y O _3-β (2)
{Wherein M ′ is one or more metal elements other than Mn and Li, and satisfies the relationship of 0 <y <1 and 0 ≦ β <1. The lithium-containing metal oxide is characterized by having a crystal in which a lithium-containing metal oxide B having a layered structure in which Li is arranged in layers is solid-solved.

  [2] The lithium-containing metal oxide according to [1], wherein M is at least Ni.

  [3] The lithium-containing metal oxide according to [1] or [2], wherein M ′ is at least Ni.

[4] The lithium-containing metal oxide A and the lithium-containing metal oxide B are represented by the following formula (3):
_{0.30 ≦ M B / (M A} + M B) ≦ 0.80 ··· (3)
{In the formula, M _A is the molar fraction of the lithium-containing metal oxide A represented by the formula (1) in the crystal constituting the lithium-containing metal oxide, and M _B is the lithium-containing metal oxide] It is the mole fraction of the lithium-containing metal oxide B represented by the above formula (2) in the crystal constituting the oxide. }, The lithium-containing metal oxide according to any one of [1] to [3].

  [5] A lithium ion secondary battery containing the lithium-containing metal oxide according to any one of [1] to [4] in a positive electrode.

[6] The following steps:
(1) Li carbonates and / or hydroxide salts and oxides, carbonates, hydroxide salts, sulfates, nitrates, hydrochlorides, and acetic acids of one or more metals other than Mn and Mn and Li By firing at least one of the salts, the following composition formula (1):
Li _{1 + k} Mn _2-x M _x O _4-α (1)
{In the formula, M is one or more metal elements other than Mn and Li, and satisfies the relations 0 ≦ k <1, 0 <x ≦ 0.5, and 0 ≦ α <1. Step for obtaining a lithium-containing metal oxide A having a spinel structure represented by: and (2) Next, the obtained lithium-containing metal oxide A and the following composition formula (4):
Li _z C _a O _b H _c (4)
{In the formula, 1 ≦ z ≦ 2, 0 ≦ a ≦ 1, 1 ≦ b ≦ 3, and 0 ≦ c ≦ 2 are satisfied. } Is mixed and fired at a temperature lower than the maximum firing temperature in the step 1, and the lithium-containing metal oxide A and the following composition formula (2):
Li ₂ Mn _1-y M ′ _y O _3-β (2)
{Wherein M ′ is one or more metal elements other than Mn and Li, and satisfies the relationship of 0 <y <1 and 0 ≦ β <1. }, A step of obtaining a crystal in which Li-containing metal oxide B having a layered structure in which Li is arranged in a layer form is dissolved;
including,
The method for producing a lithium-containing metal oxide according to any one of [1] to [4].

  [7] The method according to [6], further including a step of baking after the step (2) at a temperature higher than a maximum baking temperature in the step (2).

  The lithium-containing metal oxide according to the present invention can be suitably used as a positive electrode active material of a lithium ion secondary battery that has a high capacity and easily allows a large current to flow during discharge.

It is a schematic diagram of a spinel crystal consisting of LiMn ₂ O ₄ and LiFeMnO ₄ Metropolitan. It is a schematic diagram of the state which added Li, suppressing the movement of Mn and Fe in a spinel crystal. Li is incrementally added to the Li excess portion is a schematic diagram of a state changed to Li ₂ MO ₃ structure a layered structure.

  Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail. The following embodiments are examples for explaining the present invention, and are not intended to limit the present invention. The present invention can be implemented with appropriate modifications within the scope of the gist thereof.

[Lithium metal oxide]
The lithium-containing metal oxide according to this embodiment has the following composition formula (1):
Li _{1 + k} Mn _2-x M _x O _4-α (1)
{In the formula, M is one or more metal elements other than Mn and Li, and satisfies the relationship of 0 ≦ k <1, 0 <x ≦ 0.5, and 0 ≦ α <1. } A lithium-containing metal oxide A having a spinel structure represented by the following formula (2):
Li ₂ Mn _1-y M ′ _y O _3-β (2)
{Wherein M ′ is one or more metal elements other than Mn and Li, and satisfies the relationship of 0 <y <1 and 0 ≦ β <1. }, And a lithium-containing metal oxide B having a layered structure in which Li is arranged in layers.
Lithium-containing metal oxide.

[Lithium-containing metal oxide A]
The lithium-containing metal oxide A has the following composition formula (1):
Li _{1 + k} Mn _2-x M _x O _4-α (1)
{In the formula, M is one or more metal elements other than Mn and Li, and satisfies the relationship of 0 ≦ k <1, 0 <x ≦ 0.5, and 0 ≦ α <1. } It will not specifically limit if it is a crystal | crystallization which has a spinel structure represented by. In the case of an amorphous structure, lithium does not easily move in the oxide, so that a large current is difficult to flow in the case of a lithium ion secondary battery.

The lithium-containing metal oxide A having a spinel structure is generally a powder composed of primary particles and secondary particles in which the primary particles are aggregated. The primary particles may be single crystals themselves, or may be a combination of a plurality of single crystals with different plane orientations. The secondary particles have a form where they can be isolated as one particle without any bonding point with other particles.
The average primary particle size, which is the average particle size of the primary particles, is not particularly limited, but if the average primary particle size becomes too large, the average primary particle size of the lithium-containing metal oxide crystal finally obtained is also As a result of the increase, it becomes difficult for a large current to flow at the time of discharge. Therefore, the preferred average primary particle size is preferably 2 μm or less, more preferably 1 μm or less, and even more preferably 0.5 μm or less. However, if the average primary particle size becomes too small, the durability as a battery (long-term storage characteristics, deterioration characteristics due to repeated charge and discharge) deteriorates. Therefore, suitable average primary particles of the lithium-containing metal oxide A having a spinel structure. The diameter is preferably 0.05 μm or more, more preferably 0.1 μm or more.

When the lithium-containing metal oxide A functions as a lithium-containing metal oxide of a lithium ion secondary battery, the spinel structure is stable to charge and discharge, and most of the lithium ions contained in the structure are contained. It can be used for charging and discharging. The spinel structure may be a disordered structure belonging to the space group Fd3-m, an order structure belonging to the space group P4 ₃ 32, or a mixture of both structures. Note that “Fd3-m” should be written by adding a bar “-” on “3” of “Fd3m”.

Li _{1 + k} Mn _2-x M _x O _4-α (1)
{In the formula, M is one or more metal elements other than Mn and Li, and satisfies the relationship of 0 ≦ k <1, 0 <x ≦ 0.5, and 0 ≦ α <1. }, The value of k is 0 in a general spinel, but in the case of a spinel structure containing excessive lithium, a value of 0 <k <1 may be taken. At that time, a part or the whole of the spinel structure may be transformed into another cubic structure such as a rock salt structure, or a structure close to another crystal structure such as orthorhombic or tetragonal.
When the spinel structure represented by the composition formula (1) has one or more metal elements M other than manganese and lithium, 0.5 is usually the maximum value of x indicating the ratio of M. If more than 0.5 and one or more metal elements other than manganese and lithium are to be introduced, a structure that is not a spinel structure may be generated.
The value of α indicating the proportion of oxygen contained in the spinel structure represented by the composition formula (1) is close to zero. When α = 0, all the oxygen atoms in the spinel structure contain oxygen atoms, and there is no oxygen deficiency. However, in an actual spinel structure, oxygen deficiency is more or less often generated, and α> 0 is often obtained. However, it is difficult to form a spinel structure unless α <1.

As the metal element M constituting the lithium-containing metal oxide A, nickel (Ni), cobalt (Co), titanium (Ti), molybdenum (Mo), tungsten (W), vanadium (V ), Iron (Fe), copper (Cu), and zirconium (Zr). Among them, a metal element having a large effective nuclear charge in the 3d orbital is preferable in terms of improving the electromotive force of the lithium ion secondary battery, iron, cobalt and nickel having an effective nuclear charge of 6 or more are more preferable, and the most effective nuclear charge. Is particularly preferred.
Moreover, from the viewpoint of easily developing a high capacity, the metal element M is preferably a metal element that can take many valence states, particularly molybdenum or tungsten, which are Group 6 transition metal elements.
It is preferable that the manganese and the metal element M are uniformly dispersed in the lithium-containing metal oxide A, that is, the same kind of metal element is not aggregated. This is because if the same kind of agglomeration of metal elements exists, the agglomerated part may have a structure different from the target crystal structure.

[Lithium-containing metal oxide B]
The lithium-containing metal oxide B has the following composition formula (2):
Li ₂ Mn _1-y M ′ _y O _3-β (2)
{Wherein M ′ is one or more metal elements other than Mn and Li, and satisfies the relationship of 0 <y <1 and 0 ≦ β <1. }, There is no particular limitation as long as the crystal has a layered structure in which Li is arranged in layers. Such a structure may be a crystal structure belonging to the space group R3-m, a crystal structure belonging to the space group C2 / m, or a crystal structure belonging to the space group P3 ₁ 12. A structure in which these are mixed may be used. Note that “R3-m” should be represented by adding a bar “-” on “3” of “R3m”.

As M ′ which is one or more kinds of metal elements other than Mn and Li constituting the lithium-containing metal oxide B, nickel, cobalt, titanium, molybdenum, tungsten, vanadium, iron, copper are preferable as this embodiment. Zirconium, and nickel is particularly preferable.
The layered structure having the composition represented by the composition formula (2) has a large lithium ion content and contains the metal element M ′, thereby increasing the capacity as a lithium ion battery and providing a large current during discharge. It can be made easy to flow.
Since the value of y indicating the ratio of M ′ in the layered structure represented by the composition formula (2) is not further limited as long as the layered structure contains manganese, the range of 0 <y <1. Can take any value.
The value of β indicating the proportion of oxygen contained in the layered structure represented by the composition formula (2) is 0 or a value close to 0. When β = 0, all of the sites where oxygen atoms enter in the layered structure contain oxygen atoms, and there is no oxygen deficiency. However, in an actual layered structure, oxygen vacancies are more or less often generated and β> 0 in many cases. Further, when β> 0, a part or all of the layered structure may be deformed to be deformed into a structure different from the above-described space group. However, it is difficult to form a layered structure unless β <1.

[Crystal in which lithium-containing metal oxide A and lithium-containing metal oxide B are dissolved]
The lithium-containing metal oxide of the present invention has a crystal in which lithium-containing metal oxide A and lithium-containing metal oxide B are dissolved. In this specification, the solid solution of the lithium-containing metal oxide A and the lithium-containing metal oxide B is respectively represented by the following composition formula (1):
Li _{1 + k} Mn _2-x M _x O _4-α (1)
{In the formula, M is one or more metal elements other than Mn and Li, and satisfies the relationship of 0 ≦ k <1, 0 <x ≦ 0.5, and 0 ≦ α <1. } And the following composition formula (2):
Li ₂ Mn _1-y M ′ _y O _3-β (2)
{Wherein M ′ is one or more metal elements other than Mn and Li, and satisfies the relationship of 0 <y <1 and 0 ≦ β <1. The unit structure of each metal oxide represented by the following is a minimum unit, and each metal oxide unit composed of one or more of the minimum units is mixed and present in the crystal: Define. As a method of mixing these units in the crystal, both the lithium-containing metal oxide A and the lithium-containing metal oxide B are uniformly dispersed and mixed in a state where the size of each unit is as small as possible. Is preferred. Specifically, the sizes of the respective units are preferably 50 nm or less on average, more preferably 20 nm or less, still more preferably 10 nm or less, and particularly preferably 5 nm or less. The smaller the size of these units and the more uniformly dispersed and mixed in the crystal, the more easily a large current can flow during discharge.

  The lithium-containing metal oxide A and the lithium-containing metal oxide B are mixed with each other in the crystal by a focused ion beam (hereinafter abbreviated as FIB) or the like. It can be confirmed by processing into a thin piece of 100 nm or less and observing the atomic arrangement in the crystal using a transmission electron microscope. In particular, by using a spherical aberration correction scanning transmission electron microscope (hereinafter abbreviated as Cs-STEM) in which spherical aberration is corrected in an optical system of a transmission electron microscope, the arrangement of atoms can be observed with high resolution. The average size and the dispersion state can be obtained by image observation. In addition, by using an energy dispersive X-ray analyzer (hereinafter abbreviated as EDX) attached to Cs-STEM, the presence and distribution of metal elements M and M ′ other than lithium and manganese in each unit are confirmed. Can do.

In the lithium-containing metal oxide according to this embodiment, the abundance ratio of the lithium-containing metal oxide A and the lithium-containing metal oxide B is the mole fraction of the minimum number of units described above, and the following formula (3):
_{0.30 ≦ M B / (M A} + M B) ≦ 0.80 ··· (3)
{In the formula, M _A represents the mole fraction of the lithium-containing metal oxide A, and M _B represents the mole fraction of the lithium-containing metal oxide B. } Is preferably satisfied. Here, the relationship of the formula (3) indicates that the ratio of the lithium-containing metal oxide B is preferably 30% or more and 80% or less in terms of molar fraction, and satisfying this condition, It is possible to obtain a lithium-containing metal oxide that has a high capacity and can easily flow a large current during discharge.

  Whether or not the lithium-containing metal oxide has the target structure can be determined by a known X-ray crystal analysis method. The weight ratio of lithium and metal element in the lithium-containing metal oxide A can be determined by a known inductively coupled plasma emission analysis method (hereinafter abbreviated as ICP). Further, the average particle diameter of the crystals constituting the lithium-containing metal oxide A is obtained by measuring and averaging a plurality of crystal particle diameters in an image using a scanning electron microscope (hereinafter abbreviated as SEM). Alternatively, it can be obtained by specific surface area measurement (hereinafter abbreviated as BET) for measuring the physical adsorption method amount of an inert gas. The average particle size obtained by BET is calculated assuming that the particles are true spheres.

[Method for producing lithium metal oxide]
Although the manufacturing method of the lithium containing metal oxide in this embodiment is not specifically limited, In order to introduce | transduce the metal element M 'in the crystal structure of the lithium containing metal oxide B, for example, the following processes:
(1) Li carbonates and / or hydroxide salts and oxides, carbonates, hydroxide salts, sulfates, nitrates, hydrochlorides, and acetic acids of one or more metals other than Mn and Mn and Li By firing at least one of the salts, the following composition formula (1):
Li _{1 + k} Mn _2-x M _x O _4-α (1)
{In the formula, M is one or more metal elements other than Mn and Li, and satisfies the relations 0 ≦ k <1, 0 <x ≦ 0.5, and 0 ≦ α <1. Step for obtaining a lithium-containing metal oxide A having a spinel structure represented by: and (2) Next, the obtained lithium-containing metal oxide A and the following composition formula (4):
Li _z C _a O _b H _c (4)
{In the formula, 1 ≦ z ≦ 2, 0 ≦ a ≦ 1, 1 ≦ b ≦ 3, and 0 ≦ c ≦ 2 are satisfied. } Is mixed and fired at a temperature lower than the maximum firing temperature in the step 1, and the lithium-containing metal oxide A and the following composition formula (2):
Li ₂ Mn _1-y M ′ _y O _3-β (2)
{Wherein M ′ is one or more metal elements other than Mn and Li, and satisfies the relationship of 0 <y <1 and 0 ≦ β <1. }, A step of obtaining a crystal in which Li-containing metal oxide B having a layered structure in which Li is arranged in a layer form is dissolved;
A method for producing a lithium-containing metal oxide containing can be used.

In general, it is difficult to replace Mn in Li ₂ MnO ₃ crystals with other metal elements such as Fe, Ni, Co and the like because Li ₂ MnO ₃ crystals are more energetically more stable than Fe, Ni, Co crystals. .
In addition, when firing a precursor with a uniform metal element such as Mn, Fe, Ni, Co, etc., if the firing temperature is relatively low, the crystallinity is low and the uniformity of each metal element distribution is maintained, As the firing temperature increases, crystallization increases and domaining of each metal element easily occurs.

As described above, the present invention replaces a part of manganese of a crystal represented by the composition formula Li ₂ MnO ₃ with a different metal element, and changes the bonding mode between the metal element and oxygen accompanying the substitution, thereby changing Li ₂ The electronic state of the structure corresponding to MnO ₃ changes, the band gap in the vicinity of the Fermi level becomes smaller, the crystal changes like a conductor, and the electrical resistance decreases, so that a large current can easily flow. It was made in anticipation.
In the method for producing a lithium-containing metal oxide according to the present invention, for example, a part of the crystal manganese represented by the composition formula Li ₂ MnO ₃ can be substituted with a different metal element. This can be achieved, for example, by the following method. It should be noted that the following description of the method and FIGS. 1 to 3 used in the method are merely examples abstracted for easy understanding.
For example, when one or more kinds of metal elements M other than Mn and Li are Fe, as shown in FIG. 1, a spinel crystal containing Fe is prepared as a precursor, that is, in the step (1), Lithium-containing metal oxide A having a spinel structure is obtained, and then, in the step (2), the spinel structure obtained in the step (1) is fired at a temperature lower than the maximum firing temperature in the step (1). While maintaining the arrangement of the metal elements in the crystal of the lithium-containing metal oxide A, Li is added to the crystal (see FIG. 2), and the heating temperature is suppressed in the heating or the subsequent heating. 3, the Li-excessive portion to which Li was added in the step (2) is changed to a Li ₂ MO ₃ {in FIG. 3, M is Mn and Fe} structure, that is, the generated Li ₂ O ₃ structure that Fe remains in, possible to introduce Fe to _Li 2 MO ₃ structure.

Hereafter, the manufacturing method process of an above described lithium containing metal oxide is demonstrated in order.
[Step (1): Production of lithium-containing metal oxide A]
First, a lithium-containing metal oxide A having manganese and a metal element M is manufactured. The metal elements constituting the lithium-containing metal oxide A are preferably dispersed and distributed as uniformly as possible. The aggregation of the same kind of metal element is for reducing the discharge characteristics of the positive electrode active material.
The method for producing the lithium-containing metal oxide A is not particularly limited, and any known one can be used, and the following three examples can be given.

[Example 1]
In Example 1, as a raw material, a finely pulverized lithium salt (for example, lithium sulfate, lithium nitrate, lithium carbonate, lithium hydroxide, etc.) and two or more finely pulverized metal oxides are mixed and then fired. Is mentioned. At this time, the powder may be baked in a mixed state, may be compressed and formed into pellets, or may be baked by dispersing or dissolving the mixture in a liquid such as water. You may bake what was spray-dried by.

[Example 2]
In Example 2, lithium and two or more kinds of metal salts (for example, sulfate, nitrate, hydrochloride, acetate, etc.) are dissolved in water, a solvent such as ethylene glycol, propylene glycol, etc., and the solvent is dried up. The method of baking after performing is mentioned. In particular, it is preferable to use nitrate and acetate, and it is particularly preferable to use the mixture at a molar ratio of nitrate ion NO ₃ ^— and acetate ion CH ₃ COO ^— of 1: 3. At this time, a known complex-forming agent having a function of suppressing aggregation of the same kind of metal element during dry-up by coordination with metal ions may be added. As such a complexing agent, citric acid, acetic acid, malic acid, acetylacetone, polyvinyl alcohol and the like can be used.

[Example 3]
In Example 3, an aqueous solution of two or more kinds of metal salts (for example, sulfate, nitrate, hydrochloride, acetate, etc.) and an alkaline aqueous solution (for example, sodium carbonate, sodium bicarbonate, sodium hydroxide, hydroxide) are used as raw materials. The lithium salt described above is added to particles of poorly soluble metal salts (for example, carbonates, hydroxide salts, oxyhydroxide salts, complex salts thereof, etc.) obtained by reacting with potassium, etc. The method of baking after mixing is mentioned.
In the above reaction, in order to prevent metal ions from being oxidized by dissolved oxygen in the aqueous solution, it is preferable to react by blowing nitrogen gas, argon gas, carbon dioxide (CO ₂ ), or the like. In the case of producing a carbonate, it is preferable to employ carbon dioxide because it provides an environment in which carbonate is more easily generated.
Moreover, you may add the known complex forming agent which has the effect | action which coordinates-bonds to a metal ion and suppresses aggregation of the same kind of metal element in a hardly soluble metal salt. As such a complexing agent, ammonia, ammonium sulfate, ethylenediamine, ethylenediaminetetraacetic acid, bipyridine, diaminoethanol or the like can be used.

The firing temperature at the time of producing the lithium-containing metal oxide A is not particularly limited as long as the target lithium-containing metal oxide A is obtained, but at least 300 for the metal element and oxygen to react uniformly. ° C or higher is preferable, and 400 ° C or higher is more preferable. However, if the crystallization associated with firing proceeds too much and the average particle size of the crystal becomes too large, it becomes difficult to flow a large current during discharge as described above, and therefore it is preferably 1000 ° C. or less, more preferably 950 ° C. or less. preferable.
In the above case, firing may be performed a plurality of times at the same or different temperatures. For example, firing may be performed at 400 ° C. to 600 ° C. and then performed at 700 to 900 ° C. Multiple firings may be performed continuously with the raw material in the furnace, or after firing at a certain temperature, the raw material is taken out of the furnace and subjected to processing such as mixing, crushing, and compression again. You may bake in a furnace.

[Step (2): Lithium addition and production of solid solution of lithium-containing metal oxide A and lithium-containing metal oxide B]
Next, the lithium-containing metal oxide A obtained in the step (1) and the following composition formula (4):
Li _z C _a O _b H _c (4)
{In the formula, 1 ≦ z ≦ 2, 0 ≦ a ≦ 1, 1 ≦ b ≦ 3, and 0 ≦ c ≦ 2 are satisfied. } Is mixed, and fired at a temperature lower than the maximum firing temperature when the lithium-containing metal oxide A is produced.
This step (2) is a step of additionally introducing (adding) lithium to the lithium-containing metal oxide A. The lithium material to be additionally introduced is not particularly limited as long as lithium diffuses into the crystal of the lithium-containing metal oxide A by reacting with the lithium-containing metal oxide A, but the above-described composition formula The lithium compound C represented by (4) is preferable because lithium can be efficiently introduced. Examples of such lithium compound C include lithium carbonate, lithium hydroxide, and mixtures thereof.
In addition to the lithium compound C represented by the composition formula (4), lithium nitrate, lithium sulfate, lithium chloride, etc. may be used alone or in combination as the lithium raw material to be additionally introduced, if necessary. May be.

  When mixing the lithium-containing metal oxide A and the lithium compound C, the lithium compound C refined by pulverization or the like may be used, or the lithium compound C dissolved or dispersed in a liquid such as water is used. May be. When dissolved in a liquid such as water, the liquid may be dried up before firing, or may be fired with the liquid remaining.

In the present embodiment, the firing temperature in the step (2) of additionally introducing lithium into the lithium-containing metal oxide A needs to be in the following two lower and upper temperature ranges.
The lower limit of the firing temperature is equal to or higher than the temperature at which lithium-containing metal oxide A and lithium compound C react and lithium begins to diffuse into the crystal of lithium-containing metal oxide A. Although this temperature varies depending on the types of the lithium-containing metal oxide A and the lithium compound C, since the above reaction is generally an endothermic reaction and is accompanied by weight loss of the mixture, thermogravimetric-differential thermal analysis (Thermogravimetric-Differential). Thermal Analysis (hereinafter abbreviated as TG-DTA) is performed, and the temperature can be set by measuring the temperature at which weight loss and endothermic reaction occur. More specifically, a temperature range of −100 ° C. or higher and + 200 ° C. or lower is preferable with respect to the temperature at which the suggested heat decrease is a minimum value while showing weight loss, and more preferably in a range of −50 ° C. or higher and + 150 ° C. or lower. is there.

The upper limit of the firing temperature is not more than the maximum firing temperature in step (1). If the firing temperature exceeds this upper limit, crystal growth rapidly accelerates due to the diffusion of lithium introduced in the crystal, and the average particle diameter is in a suitable range (the preferred range is the lithium-containing metal oxidation in this embodiment). It is difficult to pass a large current during discharge.
The firing temperature in the step of additionally introducing lithium into the lithium-containing metal oxide A needs to be in the above temperature range, but it is preferable to fire near the lower limit in the above temperature range. There are many cases. When the firing temperature in the step (2) is high, diffusion of not only lithium but also a metal element occurs simultaneously in the crystal of the lithium-containing metal oxide A. As a result, a specific metal element is segregated and the desired composition / A lithium-containing metal oxide having a crystal structure may not be obtained. In the present invention, the composition formula Li ₂ MnO ₃ is increased by increasing the lithium content while maintaining the dispersion (distribution) state of the metal element in the lithium-containing metal oxide A produced in the step (1) as much as possible. Since lithium-containing metal oxide B in which a part of manganese in the crystal structure described is substituted with a different metal element is considered to be formed in lithium-containing metal oxide A, the crystal of lithium-containing metal oxide A In the step (2), it is desirable to uniformly introduce lithium into the crystal of the lithium-containing metal oxide A while suppressing the diffusion of the metal element therein. Therefore, although depending on the types of the lithium-containing metal oxide A and the lithium compound C, the firing temperature in the step (2) is generally preferably near the lower limit or slightly higher than the lower limit in the above temperature range.

  In the step of additionally introducing lithium into the lithium-containing metal oxide A, firing may be performed a plurality of times at the same or different temperatures within the above temperature range. Multiple firings may be performed continuously with the raw material in the furnace, or after firing at a certain temperature, the raw material is taken out of the furnace and subjected to processing such as mixing, crushing, and compression again. You may bake in a furnace. For example, after firing at 400 ° C. to 600 ° C., the mixture may be removed from the furnace, mixed and crushed, and then fired again at 400 ° C. to 600 ° C. The firing time at this time is not particularly limited, but is preferably 30 minutes or more, more preferably 1 hour or more in order to sufficiently complete the reaction between the lithium-containing metal oxide A and the lithium compound C. The upper limit time is not particularly limited. However, from the viewpoint of production cost, the firing time is preferably 24 hours or less, and more preferably 10 hours or less.

In the step of additionally introducing lithium into the lithium-containing metal oxide A, the crystal structure of the lithium-containing metal oxide A may be maintained, or a part or all of it may be changed to another structure. When changing to another structure, it may be a lithium-containing metal oxide B.
In the exemplified method for producing a lithium-containing metal oxide of the present embodiment, a part of the structure of the lithium-containing metal oxide A changes in the step of additionally introducing lithium into the lithium-containing metal oxide A described above. Or by additional introduction of lithium into the lithium-containing metal oxide A and subsequent firing at a higher temperature, thereby changing a part of the structure of the lithium-containing metal oxide A to obtain a predetermined proportion of lithium-containing metal oxide The product B is obtained in a state of being in solid solution with the lithium-containing metal oxide A.

  When the lithium-containing metal oxide B is obtained in the step (2) of additionally introducing lithium into the lithium-containing metal oxide A, the lithium-containing metal oxide B having sufficient crystallinity when the firing temperature is too low. May not be obtained. Moreover, the crystallinity of the lithium-containing metal oxide A may be lowered. In that case, by further firing at a temperature higher than the maximum firing temperature in the step (2) of additionally introducing lithium into the above-described lithium-containing metal oxide A, the crystallinity of the lithium-containing metal oxide in the present embodiment can be improved. Can be improved. Thereby, the average particle diameter of the crystals constituting the lithium-containing metal oxide can be adjusted to a suitable range.

[Lithium ion secondary battery]
An example of using the lithium-containing metal oxide in the present embodiment for a lithium ion secondary battery is shown below.
The lithium ion secondary battery includes a positive electrode, a negative electrode, an electrolytic solution, a separator, and an exterior body for housing them for electrical connection and insulation.
An example of the positive electrode and its manufacturing method is shown below. In general, the positive electrode preferably contains a conductive additive and a binder in addition to the lithium-containing metal oxide and the current collector foil. Here, the conductive auxiliary agent is not particularly limited as long as it is a known one that can conduct electrons, but a carbon material typified by graphite, acetylene black, and carbon black is preferable. The binder is not particularly limited as long as it can bind two or more kinds of constituent materials contained in the positive electrode, but is not limited to polyvinylidene fluoride (hereinafter abbreviated as PVDF), polytetrafluoroethylene (PTFE), polyacrylic. Polymer materials typified by acid, styrene butadiene rubber, and fluoro rubber are preferred. These are used singly or in combination of two or more. Although it does not specifically limit as current collection foil, For example, metal foil, such as aluminum, titanium, stainless steel, an expanded metal, a punch metal, a foam metal, carbon cloth, carbon paper, etc. are suitable.

  A positive electrode mixture prepared by adding a lithium-containing metal oxide and, if necessary, the above-mentioned conductive auxiliary agent or binder and mixing it in a solvent such as N-methylpyrrolidone (hereinafter abbreviated as NMP) is dispersed into a positive electrode. A mixture-containing paste is prepared. Next, this positive electrode mixture-containing paste is applied to a current collector foil and dried to form a positive electrode mixture layer, which is pressurized as necessary to adjust the thickness, thereby producing a positive electrode. In addition, a lithium containing metal oxide can be used individually by 1 type or in combination of 2 or more types.

  An example of the negative electrode and the manufacturing method thereof is shown below. A negative electrode will not be specifically limited if it acts as a negative electrode of a lithium ion secondary battery, A well-known thing can be used. It is preferable that a negative electrode contains 1 or more types chosen from the group which consists of a material which can occlude and discharge | release lithium ion as a negative electrode active material. That is, the negative electrode is lithium metal, or a negative electrode active material containing an element capable of forming an alloy with lithium, such as a carbon negative electrode active material, a silicon alloy negative electrode active material, or a tin alloy negative electrode active material, and a silicon oxide negative electrode active material. It is preferable to contain at least one negative electrode active material selected from the group consisting of a material, a tin oxide negative electrode active material, and a lithium-containing compound typified by a lithium titanate negative electrode active material. These negative electrode active materials can be used alone or in combination.

  Examples of the carbon negative electrode active material include hard carbon, soft carbon, artificial graphite, natural graphite, graphite, pyrolytic carbon, coke, glassy carbon, fired body of organic polymer compound, mesocarbon microbead, carbon fiber, activated carbon , Graphite, carbon colloid, and carbon black. Examples of coke include pitch coke, 21 dollar coke, and petroleum coke. Moreover, the fired body of an organic polymer compound is obtained by firing and carbonizing a polymer material such as a phenol resin or a furan resin at an appropriate temperature.

  Examples of a material capable of inserting and extracting lithium ions include a negative electrode active material containing an element capable of forming an alloy with lithium. The negative electrode active material may be a single metal or metalloid, an alloy or a compound, and may have at least a part of one or more of these phases. Good. In the present specification, the “alloy” includes an alloy having one or more metal elements and one or more metalloid elements in addition to an alloy composed of two or more metal elements. Further, the alloy may contain a nonmetallic element as long as it has metal properties as a whole.

Examples of metal elements and metalloid elements include titanium, tin (Sn), lead (Pb), aluminum, indium (In), silicon (Si), zinc (Zn), antimony (Sb), bismuth (Bi), Examples include gallium (Ga), germanium (Ge), arsenic (As), silver (Ag), hafnium (Hf), zirconium, and yttrium (Y).
Among these, the metal elements and metalloid elements of Group 4 or 14 in the long-period periodic table are preferable, and titanium, silicon, and tin are particularly preferable.
As an alloy of tin, for example, as a second constituent element other than tin, silicon, magnesium (Mg), nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, and Examples thereof include those having one or more elements selected from the group consisting of chromium (Cr).
Examples of the silicon alloy include, as the second constituent element other than silicon, tin, magnesium, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, and chromium. The thing which has 1 or more types of elements chosen from a group is mentioned.
As a titanium compound, a tin compound, and a silicon compound, what has oxygen or carbon is mentioned, for example, In addition to titanium, tin, or silicon, you may have the above-mentioned 2nd structural element.

A negative electrode mixture-containing paste is prepared by dispersing, in a solvent, a negative electrode mixture prepared by adding a conductive additive, a binder, or the like to the negative electrode active material as necessary. The binder is not particularly limited as long as it can bind two or more constituent materials contained in the negative electrode. Among them, carboxymethyl cellulose, styrene-butadiene crosslinked rubber latex, acrylic latex, and polyvinylidene fluoride are preferable. These are used singly or in combination of two or more.
Next, this negative electrode mixture-containing paste is applied to a current collector and dried to form a negative electrode mixture layer, which is pressurized as necessary to adjust the thickness, thereby producing a negative electrode. The current collector in the negative electrode is made of, for example, a metal foil such as a copper foil, a nickel foil, or a stainless steel foil. In addition, a negative electrode active material can be used individually by 1 type or in combination of 2 or more types.

The electrolytic solution is not particularly limited as long as it contains a lithium salt and a non-aqueous solvent and acts as an electrolytic solution of a lithium ion secondary battery, and a known one can be used.
From the viewpoint of ion conductivity, the lithium salt is preferably LiPF ₆ , LiCIO ₄ , LiAsF ₆ , Li ₂ SiF ₆ , LiOSO ₂ C _k F _{2k + 1} [k is an integer of 1 to 8], LiN (SO ₂ C _t F _{2t + 1} ) ₂ [t is an integer of 1 to 8], LiPF _n (C _t F _{2t + 1} ) _6-n [n is an integer of 1 to 5, t is an integer of 1 to 8], LiPF ₄ (C ₂ O _{2), LiPF 2 (C 2} O 2) 2, LiBF 4, LiAlO 4, LiAlCl 4, Li 2 B 12 F g H 12-g [g is an integer of from 0 to _{3], LiBF q (C s F 2s} + 1) _4-q [q is an integer of 1 to 3, s is an integer of 1 to 8], LiB (C ₂ O ₄ ) ₂ , LiBF ₂ (C ₂ O ₄ ), LiB (C ₃ O ₄ H ₂ ) ₂ , LiPF ₄ (C ₂ O ₂ ) etc. Particularly preferred is LiPF ₆ . These electrolytes can be used singly or in combination of two or more.

  Although various things can be used as a non-aqueous solvent, an aprotic polar solvent is preferable. Specific examples thereof include ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, trifluoromethylethylene carbonate, fluoroethylene. Cyclic carbonates such as carbonate and 4,5-difluoroethylene carbonate; lactones such as γ-ptyrolactone and γ-valerolactone; cyclic sulfones such as sulfolane; cyclic ethers such as tetrahydrofuran and dioxane; ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, Methyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, methyl butyl carbonate, dibutyl carbonate, ethyl pro Chain carbonates such as pyr carbonate and methyl trifluoroethyl carbonate; Nitriles such as acetonitrile; Chain ethers such as dimethyl ether; Chain carboxylic acid esters such as methyl propionate; Chain ether carbonate compounds such as dimethoxyethane It is done. These can be used individually by 1 type or in combination of 2 or more types.

As the non-aqueous solvent, it is more preferable to use a carbonate-based solvent such as cyclic carbonate and chain carbonate from the viewpoint of ion conductivity. Further, it is more preferable to use a combination of a cyclic carbonate and a chain carbonate as the carbonate solvent. Various cyclic carbonates can be used, but ethylene carbonate, propylene carbonate, and fluoroethylene carbonate are preferable, and ethylene carbonate and propylene carbonate are more preferable. Various chain carbonates can be used, but ethyl methyl carbonate, dimethyl carbonate, and diethyl carbonate are preferred.
When the carbonate solvent includes a combination of a cyclic carbonate and a chain carbonate, the mixing ratio of the cyclic carbonate and the chain carbonate is 1:10 to 5: 1 in terms of volume ratio from the viewpoint of ion conductivity. Preferably, it is 1: 5 to 3: 1.
In the case of using a carbonate-based solvent, another nonaqueous solvent such as acetonitrile or sulfolane can be further added as necessary from the viewpoint of improving battery physical properties.

  As a separator that can be used in the present embodiment, a conventionally known separator used for a lithium ion secondary battery can be used, and is not particularly limited. Among them, an insulating thin film having high ion permeability and excellent mechanical strength is preferable. Examples of such a separator include a woven fabric, a nonwoven fabric, and a synthetic resin microporous membrane, and among these, a synthetic resin microporous membrane is preferable. As the synthetic resin microporous membrane, for example, a polyolefin microporous membrane such as a microporous membrane containing polyethylene or polypropylene as a main component or a microporous membrane containing both of these polyolefins is suitably used. As the non-woven fabric, a porous film made of a heat-resistant resin such as glass-containing ceramic, polyolefin, polyester, polyamide, liquid crystal polyester, or aramid is used. The separator may be a single microporous membrane or a laminate of a plurality of microporous membranes, or may be a laminate of two or more microporous membranes.

  A conventionally well-known thing can be used for the exterior body which can be used for this embodiment, and it does not restrict | limit in particular. The material of the outer package is not particularly limited, and examples thereof include metals such as stainless steel, iron, and aluminum, or a laminate film in which the surface of the metal is coated with a resin.

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples.
Example 1 <Fe, Ni, Mn System>
<Production of lithium-containing metal oxide>
Following _Sulfate: MnSO 4 · _5H 2 O (manufactured by Kanto Chemical Co., _{Ltd.) 79.6g, NiSO 4 · 6H 2} O ( manufactured by Kanto Chemical Co., Ltd.) 26.0 g, and FeSO ₄ · _7H 2 O (Kanto Chemical stock Aqueous solution A was prepared by dissolving 3.12 g (made by company) in pure water to a total of 220 ml. An aqueous solution B was prepared by dissolving 46.6 g of sodium carbonate Na ₂ CO ₃ (manufactured by Kanto Chemical Co., Ltd.) in pure water and adding 14.6 ml of 28% by mass ammonia water (manufactured by Kanto Chemical Co., Ltd.) to a total of 220 ml.
In a reaction tank having a stirring mechanism and a mechanism for bubbling an inert gas, an aqueous solution C in which sodium sulfate Na ₂ SO ₄ (manufactured by Kanto Chemical Co., Ltd.) is dissolved in pure water to make a total of 200 ml is added, and nitrogen gas is stirred while stirring. The aqueous solution A and the aqueous solution B were simultaneously dropped into the aqueous solution C at a rate of 5 ml / min. The liquid was extracted from the reaction tank 100 ml every 10 minutes, the dropping was stopped after 40 minutes, the liquid in the reaction tank was recovered, filtered, washed with water, and dried to obtain a precipitate D.

A mixture of 2.00 g of the dried precipitate D and 0.318 g of lithium carbonate Li ₂ CO ₃ (Honjo Chemical Co., Ltd.) pulverized to an average particle size <2 μm was mixed well, and the mixture was mixed at 800 ° C. in the atmosphere. The lithium-containing metal oxide A was obtained by firing for a period of time. X-ray structural analysis revealed that the lithium-containing metal oxide A has a spinel structure.
After thoroughly mixing 1.41 g of the above lithium-containing metal oxide A and 0.286 g of the above-mentioned lithium carbonate Li ₂ CO ₃ , TG-DTA analysis was performed, and the weight loss and suggested heat from 425 ° C. It was found that the suggested decrease in heat takes a minimum value at 500 ° C. Therefore, this mixture was calcined at 650 ° C. for 5 hours in the atmosphere, lithium was additionally introduced into the oxide, and then calcined at 800 ° C. for 5 hours to obtain a lithium-containing metal oxide.

According to the X-ray structural analysis, the lithium-containing metal oxide has a spinel structure, and Li ₂ Mn _1-y M ′ _y O _{3−β that} can be assigned to the C2 / m space group. And one or more metal elements other than Li and satisfy the relationship of 0 <y <1 and 0 ≦ β <1. } Was found to have a composition of The composition ratio of the metal element obtained by acid decomposition of the lithium-containing metal oxide with microwaves (Analytic Quina Co., TOPwave (registered trademark)) and ICP measurement (Perkin Elmer Co., Optima 8300) is Li: Mn : Ni: Fe = 0.49: 0.39: 0.11: 0.01, and SEM revealed that the average particle size was about 200 μm.

<Manufacture of lithium ion secondary batteries>
Lithium-containing metal oxide obtained as described above, graphite powder (manufactured by TIMCAL, KS-6) and acetylene black powder (manufactured by Denki Kagaku Kogyo Co., Ltd., HS-100) as a conductive auxiliary agent, A polyvinylidene fluoride solution (manufactured by Kureha, L # 7208) as a binder was mixed at a solid content ratio of 80: 5: 5: 10. To the obtained mixture, NMP as a dispersion solvent was added so as to have a solid content of 30% by mass, and further mixed to prepare a slurry solution. This slurry solution was applied to one side of an aluminum foil having a thickness of 20 μm, and the solvent was removed by drying, followed by rolling with a roll press to obtain a positive electrode having a thickness of 64 μm.
LiPF ₆ was dissolved in a mixed solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 1: 2 so as to be 1 mol / L to obtain an electrolytic solution.
A lithium metal foil (thickness 0.5 mm) punched out to a diameter of 16 mm as a negative electrode is inserted into a stainless steel disk-type battery case (exterior body), and a separator made of a microporous film made of polyethylene and glass fiber is formed thereon. The separator (ADVANTEC, GA-100, film thickness: about 500 μm) was inserted, and then a positive electrode punched to a diameter of 16 mm was inserted. Next, 1.0 mL of the above-described electrolytic solution was injected therein, and after immersing the positive electrode, the negative electrode, and the separator in the electrolytic solution, the battery case was sealed to manufacture a lithium ion secondary battery.

<Battery evaluation>
The obtained lithium ion secondary battery (hereinafter, also simply referred to as “battery”) is housed in a thermostatic chamber (manufactured by Futaba Kagaku Corporation, thermostatic chamber PLM-73S) set at 25 ° C., and a charge / discharge device (Asuka Electronics) It connected to the product made by Corporation | KK Co., Ltd. charge / discharge device ACD-01). Next, the battery was charged with a constant current of 0.1 C, reached 5.0 V, charged with a constant voltage of 5.0 V for 2 hours, and discharged to 2.0 V with a constant current of 0.1 C. When the discharge capacity was measured, a capacity of 230 mAh / g was obtained. Note that 1C is a current value at which the battery is discharged in one hour.
Next, the battery was charged with a constant current of 0.3 C, reached 4.9 V, charged with a constant voltage of 4.9 V until the current became 0.05 mA or less, and then with a constant current of 2 C. When the discharge capacity when discharging to 2.0 V was measured, a capacity of 186 mAh / g was obtained.

[Comparative Example 1] <Mn-only system>
A lithium-containing metal oxide A was obtained in the same manner as in Example 1 except that only 106.1 g of MnSO ₄ .5H ₂ O (manufactured by Kanto Chemical Co., Inc.) was used as the sulfate. X-ray structural analysis revealed that the lithium-containing metal oxide A has a spinel structure.
The lithium-containing metal oxide A obtained (1.43 g) and the above-described lithium carbonate Li ₂ CO _{3 (} 0.292 g) were mixed well and fired at 650 ° C. for 5 hours in the atmosphere, and lithium was additionally introduced into the oxide. Thereafter, it was further calcined at 800 ° C. for 5 hours to obtain a lithium-containing metal oxide.

X-ray structural analysis revealed that the lithium-containing metal oxide has a spinel structure and a composition of Li ₂ MnO _{3 that} can be attributed to a C2 / m space group. The composition ratio of the metal element calculated | required by the ICP measurement similarly to Example 1 was Li: Mn = 0.97: 1, and it turned out that the average particle diameter is about 200 micrometers by SEM.
A lithium ion secondary battery was produced in the same manner as in Example 1, and the battery was charged with a constant current of 0.1 C. After reaching 5.0 V, the battery was charged with a constant voltage of 5.0 V for 2 hours. When the discharge capacity when discharged to 2.0 V with a constant current of 1 C was measured, a capacity of 147 mAh / g was obtained.
Next, the battery was charged with a constant current of 0.3 C, reached 4.9 V, charged with a constant voltage of 4.9 V until the current became 0.05 mA or less, and then with a constant current of 2 C. When the discharge capacity when discharged to 2.0 V was measured, a capacity of 87 mAh / g was obtained.

  The lithium-containing metal oxide according to the present invention has a high capacity and is suitable as a positive electrode active material for a lithium ion secondary battery that easily allows a large current to flow during discharge. It can be suitably used as a power source for various consumer devices and a power source for automobiles.

Claims (7)

The following composition formula (1):
Li _{1 + k} Mn _2-x M _x O _4-α (1)
{In the formula, M is one or more metal elements other than Mn and Li, and satisfies the relationship of 0 ≦ k <1, 0 <x ≦ 0.5, and 0 ≦ α <1. } A lithium-containing metal oxide A having a spinel structure represented by the following formula (2):
Li ₂ Mn _1-y M ′ _y O _3-β (2)
{Wherein M ′ is one or more metal elements other than Mn and Li, and satisfies the relationship of 0 <y <1 and 0 ≦ β <1. The lithium-containing metal oxide is characterized by having a crystal in which a lithium-containing metal oxide B having a layered structure in which Li is arranged in layers is solid-solved.   The lithium-containing metal oxide according to claim 1, wherein M is at least Ni.   The lithium-containing metal oxide according to claim 1, wherein M ′ is at least Ni. The lithium-containing metal oxide A and the lithium-containing metal oxide B are represented by the following formula (3):
_{0.30 ≦ M B / (M A} + M B) ≦ 0.80 ··· (3)
{In the formula, M _A is the molar fraction of the lithium-containing metal oxide A represented by the formula (1) in the crystal constituting the lithium-containing metal oxide, and M _B is the lithium-containing metal oxide] It is the mole fraction of the lithium-containing metal oxide B represented by the above formula (2) in the crystal constituting the oxide. } The lithium containing metal oxide of any one of Claims 1-3 which satisfy | fills the relationship of}.   The lithium ion secondary battery which contains the lithium containing metal oxide of any one of Claims 1-4 in a positive electrode. The following steps:
(1) Li carbonates and / or hydroxide salts and oxides, carbonates, hydroxide salts, sulfates, nitrates, hydrochlorides, and acetic acids of one or more metals other than Mn and Mn and Li By firing at least one of the salts, the following composition formula (1):
Li _{1 + k} Mn _2-x M _x O _4-α (1)
{In the formula, M is one or more metal elements other than Mn and Li, and satisfies the relations 0 ≦ k <1, 0 <x ≦ 0.5, and 0 ≦ α <1. Step for obtaining a lithium-containing metal oxide A having a spinel structure represented by: and (2) Next, the obtained lithium-containing metal oxide A and the following composition formula (4):
Li _z C _a O _b H _c (4)
{In the formula, 1 ≦ z ≦ 2, 0 ≦ a ≦ 1, 1 ≦ b ≦ 3, and 0 ≦ c ≦ 2 are satisfied. } Is mixed and fired at a temperature lower than the maximum firing temperature in the step 1, and the lithium-containing metal oxide A and the following composition formula (2):
Li ₂ Mn _1-y M ′ _y O _3-β (2)
{Wherein M ′ is one or more metal elements other than Mn and Li, and satisfies the relationship of 0 <y <1 and 0 ≦ β <1. }, A step of obtaining a crystal in which Li-containing metal oxide B having a layered structure in which Li is arranged in a layer form is dissolved;
including,
The manufacturing method of the lithium containing metal oxide of any one of Claims 1-4.   The method according to claim 6, further comprising, after the step (2), firing at a temperature higher than the maximum firing temperature in the step (2).

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