JP6322012B2 - Lithium-containing composite oxide, method for producing the same, positive electrode active material containing the composite oxide, and non-aqueous lithium ion secondary battery - Google Patents

Description

  The present invention relates to a lithium-containing composite oxide useful as a positive electrode active material for a non-aqueous lithium ion secondary battery and a method for producing the same.

Non-aqueous secondary batteries containing lithium-containing composite oxides are characterized by their light weight, high energy, and long life, and as power sources for portable electronic devices such as notebook computers, mobile phones, digital cameras, and video cameras. Widely used. In addition, with the shift to a low environmental impact society, hybrid electric vehicles (hereinafter abbreviated as “HEV”) and plug-in HEVs (hereinafter abbreviated as “PHEV”). ) And power storage fields such as residential power storage systems.
When a non-aqueous lithium ion secondary battery is mounted on a vehicle or residential power storage system such as an automobile, from the viewpoint of cycle performance and long-term reliability, the constituent materials of the battery are chemically and electrochemically stable. Materials with excellent strength and corrosion resistance are required. Furthermore, high electrical capacity and high output performance are also required as non-aqueous secondary batteries as necessary physical properties.

By the way, as a positive electrode material of a non-aqueous lithium ion secondary battery, rock salt layer type positive electrode materials such as LiCoO ₂ and LiNiO ₂ , spinel type positive electrode materials such as LiMn ₂ O ₄ , and olivine type positive electrode materials such as LiFePO ₄ are known. It has been. The layered compound LiCoO ₂ , which is a typical positive electrode material, is relatively expensive, and if the Li is pulled out by 50% or more during charge / discharge, the layered structure collapses. There is a problem in terms of.
In addition, the theoretical capacity of an olivine-type positive electrode material such as LiFePO ₄ is about 170 mAh / g, whereas a positive electrode material of about 150 mAh / g has already been used, and there is almost no room for further capacity improvement. .
Further, it is electrochemically inactive with Li ₂ M′O ₃ (M ′ represents a metal ion having an average oxidation number of 4), which is electrochemically inactive but has a high theoretical capacity of about 460 mAh / g. There is also a disclosure of a technique for obtaining a high electric capacity by an Li-excess solid solution in combination with an active LiMO ₂ (M represents a metal ion having an average oxidation number of trivalent).

For example, in the following Patent Document 1, xLiMO ₂ (1-x) Li ₂ M′O ₃ (x is in the range of 0 <x <1 and M is at least one average including Ni. And a composition of LiMO ₂ and Li ₂ M′O ₃ , wherein M ′ is one or more metal ions having an average oxidation number of 4 containing at least Mn. A layered compound is disclosed.
Further, in Patent Document 2 below, xLiMO ₂ (1-x) Li ₂ M′O ₃ (x is in the range of 0 <x <1, and M is an average oxidation number trivalent containing at least Mn. I represents an ion, and M ′ includes an ion having an average oxidation number of 4 valence.), And a layered compound having a composition of LiMO ₂ and Li ₂ M′O ₃ is disclosed.
Furthermore, the following Patent Document 3 discloses a technique for combining F, Cl, and I with Ni, Co, and Mn as essential components, all of which have a high electric capacity.
Furthermore, the following Patent Documents 4, 5 and 6 have a structure represented by xLiMO ₂ (1-x) Li ₂ M′O ₃ , and Li _{1 + a} Ni _α Mn _β Co _γ O ₂ (a, α, β and γ are compositions of 0.05 <a <0.25, 0.1 <α <0.4, 0.4 <β <0.65, 0.05 <γ <0.3, respectively. It is disclosed that a particularly high electric capacity can be obtained in the case of a Li _1.2 Ni _0.175 Co _0.10 Mn _0.525 O ₂ composition.

However, the above Li-excess solid solution has a problem that the discharge rate characteristics are poor due to the low conductivity of the Li ₂ M′O ₃ component. In order to solve this problem, as an attempt to improve the rate characteristics by increasing the conductivity of the Li-excess solid solution surface, for example, the following Patent Document 7 discloses a technique for coating an indium-based compound, A technique for coating a conductive carbon is reported in Non-Patent Document 1 below.
On the other hand, in order to improve the conductivity of the Li ₂ M′O ₃ structure with low conductivity, the tetravalent Mn of the Li ₂ M′O ₃ structure is reduced to highly conductive trivalent Mn by a reduction technique using hydrogen. The following Non-Patent Document 2 proposes an attempt to improve the conductivity.

US Pat. No. 6,667,082 US Pat. No. 6,680,143 US Pat. No. 7,135,252 Special table 2011-519126 gazette Special table 2012-504316 gazette Special table 2012-505520 gazette JP 2013-201119 A

Electrochemistry Communications 12 (2010) 750-753 Electrochemical and Solid-State Letters 14 (9) A126-A129 (2011)

As described above, when the reduction treatment described in Non-Patent Document 2 reduces the Mn valence of the Li ₂ M ′ (Mn) O ₃ structure and reduces the Li-excess solid solution, the effect of improving the discharge rate characteristics is achieved. Is insufficient, or the reduction of the crystal structure due to excessive reduction proceeds and there is a problem that a sufficient discharge capacity cannot be obtained. Therefore, although all of the conventional techniques have a certain level of discharge rate improvement effect, they are not sufficient, and there has been a demand for a positive electrode active material having a high electric capacity and excellent discharge rate characteristics.
Under such circumstances, the problem to be solved by the present invention is that when used as a positive electrode active material, a composite oxide that can be a non-aqueous lithium ion secondary battery that can achieve both high discharge capacity and high discharge rate characteristics, and It is to provide a method for producing the composite oxide.

  As a result of earnestly researching and solving experiments to solve the above problems, the present inventor kept a Li-excess solid solution in a specific reduction state and a specific crystal state, and when this was used as a positive electrode active material, a high discharge was obtained. The present inventors have found that a composite oxide that can be a non-aqueous lithium ion secondary battery that can achieve both capacity and high discharge rate characteristics can be obtained, and thus the present invention has been achieved.

That is, the present invention is as follows.
[1] The following general formula:
Li [Li _X Ni _a Mn _b Co _c ] O _2-σ
{Where x + a + b + c = 1, 0.05 <x <0.3, 0 <a <0.3, 0 <b <0.65, 0 <c <0.3, and 0.01 <σ <0 .05. } And the crystal plane diffraction intensities of the (003) plane and (104) plane in X-ray diffraction measurement are I (003) and I (104), respectively, 1.6 <I (003) / A composite oxide having a layered structure characterized by I (104) <4.0.

  [2] The composite oxide according to [1], wherein 0.08 ° <H (003) <0.13 ° when the half width of the (003) plane is H (003).

  [3] The above [1], wherein 0.1 <x <0.25, 0.15 <a <0.2, 0.4 <b <0.55, and 0.05 <c <0.2 Or the composite oxide according to [2].

  [4] The composite oxide according to any one of [1] to [3], wherein 0.015 <σ <0.04.

  [5] The composite oxide according to any one of [1] to [4], wherein 1.8 <I (003) / I (104) <2.5.

[6] The following:
The following general formula:
Li [Li _x Ni _a Mn _b Co _c ] O _2-σ
{Where x + a + b + c = 1, 0.005 <x <0.3, 0 <a <0.3, 0 <b <0.65, 0 <c <0.3, and −0.04 <σ ≦ 0.01. A step of reducing a composite oxide having a layered structure represented by
The manufacturing method of the complex oxide in any one of said [1]-[5] containing.

  [7] The method according to [6], wherein the hydrocarbon is a hydrocarbon having 1 to 5 carbon atoms.

  [8] The method according to [7], wherein the hydrocarbon is at least one selected from the group consisting of methane, ethane, ethylene, propane, propylene, and butane.

  [9] The method according to [8], wherein the hydrocarbon is propylene.

  [10] A positive electrode active material comprising the composite oxide according to any of [1] to [5] or the composite oxide according to any of [6] to [9].

  [11] A non-aqueous lithium ion secondary battery including the positive electrode active material according to [10].

  The composite oxide according to the present invention can maintain both a high discharge capacity and a high discharge rate characteristic when the Li excess solid solution is used as a positive electrode active material by maintaining a specific reduction state and a specific crystal state. It can be set as a water-system lithium ion secondary battery.

It is sectional drawing which shows roughly an example of the non-aqueous secondary battery in this embodiment.

Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail. The present invention is not limited to the following embodiments, and various modifications can be made within the scope of the invention. In addition, the range described using "-" in this specification includes the numerical value described before and behind that.
The composite oxide in this embodiment has the following general formula:
Li [Li _X Ni _a Mn _b Co _c ] O _2-σ
{Where x + a + b + c = 1, 0.05 <x <0.3, 0 <a <0.3, 0 <b <0.65, 0 <c <0.3, and 0.01 <σ <0 .05. } And the crystal plane diffraction intensities of the (003) plane and (104) plane in X-ray diffraction measurement are I (003) and I (104), respectively, 1.6 <I (003) / A complex oxide having a layered structure characterized by I (104) <4.0.

The composite oxide in the present embodiment is useful as a positive electrode active material for a non-aqueous lithium ion secondary battery. In the present embodiment, the diffraction intensity obtained by the X-ray diffraction measurement is a value before charging the battery.
The range of x is 0.05 <x <0.3, preferably 0.1 <x <0.25. When x is larger than 0.05, sufficient electric capacity can be obtained, and when it is smaller than 0.3, excessive Li can be taken into the crystal structure, and excessive Li is prevented from becoming a resistance factor. be able to.
The range of a is 0 <a <0.3, preferably 0.15 <a <0.2. By making a larger than 0, the crystal structure can be stabilized, and by making it smaller than 0.3, cycle characteristics can be improved, the charging voltage can be increased, and the discharge capacity can be increased.

The range of b is 0 <b <0.65, preferably 0.4 <b <0.55. When b is larger than 0, a high electric capacity can be obtained, and when it is smaller than 0.65, the resistance becomes small and a sufficient electric capacity can be utilized.
The range of c is 0 <c <0.3, preferably 0.05 <c <0.2. When c is larger than 0, the crystal structure is stabilized, cycle characteristics are improved, and when it is smaller than 0.3, a sufficient electric capacity can be obtained.
σ represents the amount of oxygen deficiency, and can be obtained by ordinary chemical analysis such as spectroscopic methods, elemental analysis, and titration.
In this embodiment, a composite oxide having a layered structure in which a lithium layer, an oxygen layer, and a transition metal layer are stacked is used. If σ is within a predetermined range and the amount of oxygen deficiency is a desirable amount, there is no effect on the crystal structure, transition metal reduction occurs due to charge compensation due to oxygen deficiency, and the valence of the transition metal decreases, so that the conductivity of the crystal improves. On the other hand, when σ is out of the predetermined range and is a small value, the crystal structure is not affected at all, but the degree of reduction of the transition metal is not sufficient, and the effect of improving the conductivity of the desired crystal cannot be obtained. When the value becomes larger than the predetermined range, the transition metal is excessively reduced, and the conductivity behavior is changed to cause a resistance factor. Further, the oxygen deficiency in the oxygen layer increases, A part of the transition metal falls and transitions to a different crystal phase, or the collapse of the oxygen layer causes so-called “crystal degradation” that the crystallinity is remarkably lowered, and the conductivity is significantly lowered. Therefore, the range of σ is 0.01 <σ <0.05, and preferably 0.015 <σ <0.04. When it is larger than 0.01, a sufficient discharge rate improvement effect is obtained, and when it is smaller than 0.05, a sufficient electric capacity can be obtained by suppressing the deterioration of the crystal structure.

  In the X-ray diffraction (XRD) measurement, a diffraction pattern of 2θ values is read in an X-ray diffraction analysis obtained using CuKα rays as an X-ray source for the counter cathode. For the intensity of each peak, a perpendicular line is drawn from the peak top with a line connecting points without peaks in the diffraction pattern as the base line, and the length of the line segment intersecting with the base line is obtained as the intensity. The half width is indicated by the width of the peak shape when the peak is horizontally cut at a value half the peak intensity from the baseline in the diffraction pattern in which the horizontal axis represents 2θ and the vertical axis represents the diffraction intensity. . In addition, the above “point without a peak” means a point on a so-called baseline in a chart in which the vertical axis represents diffraction X-ray intensity and the horizontal axis represents 2θ in XRD measurement. Indicates. Usually, XRD measurement includes a certain level of noise and the like, and therefore shows a certain level of diffracted X-ray intensity even at a point where there is no peak (no diffraction point). Therefore, it is possible to mechanically obtain a line with almost zero diffracted X-ray intensity by calculation of the measuring instrument (calculate noise and background from the entire analysis result), and use this as the baseline.

In the composite oxide in this embodiment, when the crystal plane diffraction intensities of the (003) plane and the (104) plane are I (003) and I (104), respectively, the ratio of I (003) to I (104) is 1.6 <I (003) / I (104) <4.0, preferably 1.8 <I (003) / I (104) <2.5.
In this embodiment, Ni-containing composite oxide is used. In the layered complex oxide containing Ni, Ni is relatively easily reduced to divalent, and since the ion radii of Li ⁺ and Ni ²⁺ are almost equal, Ni ²⁺ is partially replaced with Li ^{+ in the} lithium layer. It is easy to become. When even part of the lithium layer is mixed with Ni ²⁺ , the region becomes an irregularly arranged rock salt phase having an irregular arrangement. This irregularly arranged rock salt phase is electrically inactive. In addition, since Ni ²⁺ present in the lithium layer inhibits two-dimensional diffusion of lithium ions, the layered composite oxide in which Ni ²⁺ enters the lithium layer has a markedly reduced electric capacity. The presence of this irregularly arranged rock salt phase is, for example, the diffraction intensity of the (003) plane in the powder X-ray diffraction measurement as shown in the battery handbook (2010, published by Ohm Co., Ltd. p.432) (104 The ratio with the diffraction intensity of the surface) can be used as an index. The (003) plane strength reflects the degree of development of the layered structure, and if I (003) / I (104) increases, it means that the growth of the irregularly arranged rock salt phase is small, while I (003) When / I (104) is larger than the predetermined range, the specific surface area of the particles is decreased due to excessive crystal growth, and the electric capacity is decreased. Therefore, there is a preferable range for I (003) / I (104). In the present embodiment, specifically, a sufficiently grown crystal can be obtained by making I (003) / I (104) larger than 1.6, the deterioration of the crystal can be suppressed, and a sufficient electric capacity can be obtained. Further, by making it smaller than 4.0, the specific surface area is increased, and a sufficient electric capacity can be obtained.
I (003) / I (104) can be adjusted by changing the firing temperature, and decreases with decreasing temperature, and conversely increases with increasing temperature. Adjustment can also be made by changing σ. When σ increases, I (003) / I (104) tends to decrease, and when σ decreases, I (003) / I (104) tends to increase. is there. In the present embodiment, I (003) / I (104) is appropriately adjusted and used within a preferable range.

In the present embodiment, when the half width of the (003) plane is H (003), it is preferably in the range of 0.08 ° <H (003) <0.13 °, more preferably 0. 1 ° <H (003) <0.12 °. When H (003) is larger than 0.08 °, a sufficient specific surface area can be obtained, and the cycle characteristics tend to be improved, and when it is smaller than 0.13 °, sufficient complex oxide crystal growth is obtained. This increases the electric capacity.
H (003) can be adjusted by changing the firing temperature. The value decreases as the firing temperature is increased, and conversely, the value increases as the firing temperature is lowered.

In the production of the composite oxide in this embodiment, after producing a constant ratio of the composite oxide, oxygen can be desorbed by reduction treatment to obtain an oxygen-deficient composite oxide. Here, the constant ratio composite oxide is, for example, a composite oxide obtained by firing with normal air or an oxygen-containing gas, and means a composite oxide having no oxygen deficiency.
There is no particular limitation on the method for producing the fixed ratio composite oxide, and a commonly used production method can be used. From the viewpoint of uniformly distributing elements and obtaining high battery performance, a sol-gel method, a coprecipitation method, and a combustion method using a combustible gel are preferably used. For example, in the coprecipitation method, a homogeneous precursor is obtained by coprecipitation as a carbonate using various metal sulfates other than Li, and after purification and separation, Li raw materials such as Li carbonate are mixed and fired. As a result, a composite oxide having a desired constant ratio can be obtained and preferably used.

The reduction treatment method is not particularly limited as long as a desired composition and crystal state can be obtained, and a commonly used reduction method using a gas phase or a liquid phase can be used. From the viewpoint of ease of adjustment of the degree of reduction and suppression of deterioration due to reduction of the composite oxide crystal, a gas phase reduction method is preferably used. In the reduction by the gas phase, for example, the reduction treatment can be performed by bringing a reducing gas into contact with an inert gas under heating. The heating temperature is 50 ° C to 800 ° C, preferably 200 ° C to 400 ° C. By setting the heating temperature to 50 ° C. or higher, reduction treatment for obtaining a preferable σ can be carried out efficiently, and by setting the heating temperature to 800 ° C. or lower, deterioration of the composite oxide crystal can be suppressed. The reduction treatment time is in the range of 1 minute to 24 hours, preferably in the range of 0.5 hour to 10 hours. By making the reduction treatment time 1 minute or more, the composite oxide is uniformly reduced, and a sufficient reduction treatment effect can be obtained, and by making the reduction treatment time 24 hours or less, the reduction treatment can be performed efficiently, Degradation of the composite oxide can also be suppressed. As the reducing gas, a reducing gas such as hydrogen, CO, or hydrocarbon can be used as long as a desired composition and crystal state can be obtained. From the viewpoint of suppressing deterioration of the composite oxide, a hydrocarbon is preferably used, more preferably a hydrocarbon having 1 to 5 carbon atoms because it can be easily handled as a gas and can be easily used in a reduction method by a gas phase. More preferably, methane, ethane, ethylene, propane, propylene, or butane is used from the viewpoint of easy availability and economy, and there is a high tendency to suppress the deterioration of the composite oxide. Propylene is most preferably used from the viewpoint that it can be easily used. The reducing gas can be used after being diluted with an inert gas such as N ₂ , Ar, or He for the purpose of suppressing deterioration of the composite oxide due to reduction and obtaining a preferable σ range. It is 0 volume%-90 volume%, Preferably it is 0.1 volume%-10 volume%.

When the reduction is performed in the gas phase, σ can be adjusted by changing the type of the reducing agent, the concentration of the reducing agent, the reduction treatment temperature, and the reduction treatment time.
The σ of the composite oxide is determined from the constituent element ratio, spectroscopic methods such as X-ray photoelectron spectroscopy (XPS), electron energy loss spectroscopy (EELS), powder X-ray, X-ray absorption fine structure method (XAFS), etc. For example, the composition ratio of metals is determined by atomic absorption spectrometry, the average valence of transition metals is determined by titration, and the amount of oxygen necessary for charge compensation is calculated from the atomic composition ratio and average valence. , Σ can also be obtained.
The number average particle diameter (primary particle diameter) of the composite oxide is not particularly limited, but is preferably 0.05 μm to 100 μm, more preferably 1 μm to 10 μm. When the number average particle size of the composite oxide is in the above range, there is a tendency that the balance between homogeneity and packing density tends to be good when the electrode is produced. In addition, a sufficient electrode capacity can be obtained as a battery by increasing the filling amount of the positive electrode active material of the battery when the particle diameter is 100 μm or less.

<Non-aqueous lithium ion secondary battery>
The non-aqueous lithium ion secondary battery in the present embodiment is a battery using the above-described composite oxide as a positive electrode active material, for example, a lithium ion secondary battery schematically showing a cross-sectional view in FIG. A lithium ion secondary battery 100 shown in FIG. 1 includes a separator 110, a positive electrode 120 and a negative electrode 130 sandwiching the separator 110 from both sides, and a positive electrode current collector 140 (arranged outside the positive electrode) sandwiching the laminate. And negative electrode current collector 150 (disposed on the outside of the negative electrode) and a battery exterior 160 for housing them. A laminate in which the positive electrode 120, the separator 110, and the negative electrode 130 are stacked is impregnated with an electrolytic solution. As each of these members, those similar to those provided in a conventional lithium ion secondary battery can be used except that the composite oxide of the present embodiment is used as a positive electrode active material. Can be.

<Positive electrode>
The positive electrode is not particularly limited as long as the composite oxide of the present embodiment is used as a positive electrode active material and acts as a positive electrode of a non-aqueous secondary battery. For example, the positive electrode can be obtained as follows.
First, a positive electrode mixture-containing paste is prepared by dispersing, in a solvent, a positive electrode mixture obtained by adding a conductive additive, a binder, or the like to the positive electrode active material as necessary. Next, this positive electrode mixture-containing paste is applied to a positive electrode current collector and dried to form a positive electrode mixture layer, which is pressurized as necessary, and the thickness is adjusted to produce a positive electrode. In producing the positive electrode, examples of the conductive aid used as necessary include carbon black and carbon fiber typified by graphite, acetylene black and ketjen black. The number average particle diameter (primary particle diameter) of the conductive assistant is preferably 10 nm to 10 μm, more preferably 20 nm to 1 μm. Examples of the binder include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid, styrene butadiene rubber, and fluorine rubber.
Here, the solid content concentration in the positive electrode mixture-containing paste is preferably 30 to 80% by mass, and more preferably 40 to 70% by mass. The positive electrode current collector is made of, for example, a metal foil such as an aluminum foil or a stainless steel foil, and may be a carbon coating or a mesh.

<Negative electrode>
The negative electrode is not particularly limited as long as it functions as a negative electrode of a non-aqueous lithium ion secondary battery, and a known one can be used. The negative electrode preferably contains at least one material selected from the group consisting of a material capable of inserting and extracting lithium ions as a negative electrode active material and metallic lithium. Examples of such materials include lithium metal, amorphous carbon (hard carbon), artificial graphite, natural graphite, graphite, pyrolytic carbon, coke, glassy carbon, organic polymer compound fired body, mesocarbon microbeads. Carbon materials represented by carbon fiber, activated carbon, graphite, carbon colloid, and carbon black. Among these, examples of the coke include pitch coke, needle 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. In addition to carbon, the carbon material may contain heterogeneous compounds such as O, B, P, N, S, SiC, and B ₄ C. As content of a different compound, it is preferable that it is 0-10 mass%.
Further, examples of the material capable of inserting and extracting lithium ions include a material containing an element capable of forming an alloy with lithium. This material may be a single metal or a semi-metal, an alloy or a compound, and may have at least a part of one or more of these phases. Good.

The number average particle diameter (primary particle diameter) of the negative electrode active material is preferably 0.1 μm to 100 μm, more preferably 1 μm to 10 μm.
A negative electrode is obtained as follows, for example.
First, a negative electrode mixture-containing paste is prepared by dispersing, in a solvent, a negative electrode mixture prepared by adding a conductive additive or a binder to the negative electrode active material, if necessary. Next, this negative electrode mixture-containing paste is applied to a negative electrode 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.
Here, the solid content concentration in the negative electrode mixture-containing paste is preferably 30 to 80% by mass, and more preferably 40 to 70% by mass. The negative electrode current collector is made of a metal foil such as a copper foil, a nickel foil, or a stainless steel foil.
Examples of the conductive aid used as necessary in the production of the negative electrode include carbon black and carbon fiber typified by graphite, acetylene black, and ketjen black. The number average particle diameter (primary particle diameter) of the conductive assistant is preferably 0.1 μm to 100 μm, more preferably 1 μm to 10 μm. Examples of the binder include PVDF, PTFE, polyacrylic acid, styrene butadiene rubber, and fluorine rubber.

<Electrolyte>
In the case of a lithium ion secondary battery, the electrolyte solution in the present embodiment is not particularly limited as long as it contains at least a non-aqueous solvent and a lithium salt and acts as an electrolyte solution for a non-aqueous secondary battery. Things can be used. The electrolyte solution preferably does not contain moisture, but may contain a very small amount of moisture as long as it does not inhibit the desired effect. Such water content is, for example, 0 to 100 ppm with respect to the total amount of the electrolytic solution.
There is no restriction | limiting in particular as a non-aqueous solvent, For example, an aprotic solvent is mentioned, Among these, an aprotic polar solvent is preferable. Specific examples of the non-aqueous solvent include, for example, ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, trans-2,3-butylene carbonate, cis-2,3-butylene carbonate, 1,2-pentylene carbonate, Trans-2,3-pentylene carbonate, cis-2,3-pentylene carbonate, trifluoromethylethylene carbonate, fluoroethylene carbonate, cyclic carbonate represented by 1,2-difluoroethylene carbonate; γ-butyrolactone, γ- Lactones typified by valerolactone; sulfur compounds typified by sulfolane and dimethyl sulfoxide; cyclic ethers typified by tetrahydrofuran, 1,4-dioxane and 1,3-dioxane; methyl ethyl carbonate, dimethyl Chain carbonates represented by til carbonate, diethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, methyl butyl carbonate, dibutyl carbonate, ethyl propyl carbonate, methyl trifluoroethyl carbonate; acetonitrile, propiononitrile, butyronitrile, Mononitriles such as valeronitrile and acrylonitrile; alkoxy-substituted nitriles represented by methoxyacetonitrile and 3-methoxypropionitrile; cyclic nitriles represented by benzonitrile; ethers represented by dimethyl ether; represented by methyl propionate A chain ether carbonate compound represented by dimethoxyethane. Moreover, the halides represented by these fluorides, etc. are mentioned. These are used singly or in combination of two or more.

In order to increase the ionization degree of the lithium salt that contributes to charging / discharging of the non-aqueous lithium ion secondary battery, the non-aqueous solvent preferably contains one or more cyclic aprotic polar solvents, and contains one or more cyclic carbonates. It is more preferable. Moreover, it is preferable that it is a mixed solvent of the said 2 or more types of said non-aqueous solvent from a viewpoint of making all the solubility, conductivity, and ionization degree of lithium salt favorable.
The lithium salt is not particularly limited as long as it is used in an electrolyte solution for a non-aqueous secondary battery, and any lithium salt may be used. The lithium salt is preferably contained in the nonaqueous electrolytic solution at a concentration of 0.1 to 3 mol / L, and more preferably 0.5 to 2 mol / L. When the concentration of the lithium salt is within the above range, the electric conductivity of the electrolytic solution is kept high, and at the same time, the charge / discharge efficiency of the nonaqueous secondary battery tends to be kept high.

The lithium salt in the present embodiment is not particularly limited, but is preferably an inorganic lithium salt. The inorganic lithium salt is not particularly limited as long as it is used as a normal non-aqueous electrolyte, and any one may be used. Specific examples of such inorganic lithium salts include, for example, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , Li ₂ SiF ₆ , LiSbF ₆ , LiAlO ₄ , LiAlCl ₄ , Li ₂ B ₁₂ F _b H _12-b. [B is an integer of 0 to 3] and lithium salt bonded to a polyvalent anion.
These inorganic lithium salts are used singly or in combination of two or more. Among these, when an inorganic lithium salt having a fluorine atom is used as the inorganic lithium salt, a passive film is formed on the surface of the positive electrode current collector foil, which is preferable from the viewpoint of suppressing an increase in internal resistance. Moreover, since it tends to be easily released to free fluorine atom, as the inorganic lithium salt, inorganic lithium salt is more preferred to have a phosphorus atom, LiPF ₆ is particularly preferred.
The content of the inorganic lithium salt is preferably 0.1 to 40% by mass, more preferably 1 to 30% by mass, and 5 to 25% by mass with respect to the total amount of the non-aqueous electrolyte solution. Is more preferable.

  In the case of a lithium ion secondary battery, the non-aqueous electrolyte in the present embodiment only needs to contain at least a non-aqueous solvent and a lithium salt, but may further contain an additive. The additive is not particularly limited as long as it does not hinder the effects of the present invention, and may substantially overlap with a substance that plays a role as a solvent for dissolving a lithium salt, that is, the above non-aqueous solvent. Good. In addition, the additive is preferably a substance that contributes to the performance improvement of the non-aqueous electrolyte solution and the non-aqueous secondary battery in the present embodiment, but also includes substances that are not directly involved in the electrochemical reaction, One component is used alone, or two or more components are used in combination.

Specific examples of the additive include, for example, 4-fluoro-1,3-dioxolan-2-one, 4,4-difluoro-1,3-dioxolan-2-one, cis-4,5-difluoro-1, 3-dioxolan-2-one, trans-4,5-difluoro-1,3-dioxolan-2-one, 4,4,5-trifluoro-1,3-dioxolan-2-one, 4,4,5 , 5-tetrafluoro-1,3-dioxolan-2-one, fluoroethylene carbonate represented by 4,4,5-trifluoro-5-methyl-1,3-dioxolan-2-one; vinylene carbonate, 4 , 5-Dimethyl vinylene carbonate, cyclic carbonate containing unsaturated bond typified by vinyl ethylene carbonate; γ-butyrolactone, γ-valerolactone, γ-caprolacto , Δ-valerolactone, δ-caprolactone, lactone represented by ε-caprolactone; cyclic ether represented by 1,2-dioxane; methyl formate, methyl acetate, methyl propionate, methyl butyrate, ethyl formate , Ethyl acetate, ethyl propionate, ethyl butyrate, n-propyl formate, n-propyl acetate, n-propyl propionate, n-propyl butyrate, isopropyl formate, isopropyl acetate, isopropyl propionate, isopropyl Butyrate, n-butyl formate, n-butyl acetate, n-butyl propionate, n-butyl butyrate, isobutyl formate, isobutyl acetate, isobutyl propionate, isobutyl butyrate, se -Butyl formate, sec-butyl acetate, sec-butyl propionate, sec-butyl butyrate, tert-butyl formate, tert-butyl acetate, tert-butyl propionate, tert-butyl butyrate, methyl pivalate , N-butyl pivalate, n-hexyl pivalate, n-octyl pivalate, dimethyl oxalate, ethyl methyl oxalate, diethyl oxalate, diphenyl oxalate, malonic acid ester, fumaric acid ester, maleic acid ester Acid esters; amides represented by N-methylformamide, N, N-dimethylformamide, N, N-dimethylacetamide; ethylene sulfite, propylene sulfite, butylene sulfite, pentenser Cyclic sulfur compounds typified by sulfite, sulfolane, 3-methylsulfolane, 3-sulfolene, 1,3-propane sultone, 1,4-butane sultone, 1,3-propanediol sulfate, tetramethylene sulfoxide, thiophene 1-oxide An aromatic compound typified by monofluorobenzene, biphenyl, and fluorinated biphenyl; a nitro compound typified by nitromethane; a Schiff base; a Schiff base complex; and an oxalato complex. These are used singly or in combination of two or more.
Although there is no restriction | limiting in particular about content of the additive in the non-aqueous electrolyte in this embodiment, It is preferable that it is 0.1-30 mass% with respect to the whole quantity of a non-aqueous electrolyte, 0.1-10 mass % Is more preferable.

<Separator>
The non-aqueous lithium ion secondary battery in the present embodiment preferably includes a separator between the positive electrode and the negative electrode from the viewpoint of providing safety such as prevention of short circuit between the positive and negative electrodes and shutdown. The separator may be the same as that provided for a known non-aqueous secondary battery, and is preferably an insulating thin film having high ion permeability and excellent mechanical strength. Examples of the separator include a woven fabric, a nonwoven fabric, and a synthetic resin microporous membrane. Among these, a synthetic resin microporous membrane is preferable. As the synthetic resin microporous membrane, for example, a microporous membrane containing polyethylene or polypropylene as a main component or a polyolefin microporous membrane such as a microporous membrane containing both of these polyolefins is preferably used. As the nonwoven fabric, a porous film made of a heat-resistant resin such as 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.

<Production method of battery>
The non-aqueous lithium ion secondary battery in the present embodiment is manufactured by a known method using the above-described non-aqueous electrolyte, a positive electrode manufactured using the composite oxide, a negative electrode, and, if necessary, a separator. For example, a plurality of positive electrodes in which a positive electrode and a negative electrode are wound in a laminated state with a separator interposed therebetween to be formed into a laminate having a wound structure, or they are alternately laminated by bending or laminating a plurality of layers. Or a laminate in which a separator is interposed between the electrode and the negative electrode. Next, the laminated body is accommodated in the battery case (exterior), the electrolytic solution is poured into the case, and the laminated body is immersed in the electrolytic solution and sealed to thereby seal the non-aqueous secondary of this embodiment. A battery can be fabricated. Alternatively, an electrolyte membrane containing a gelled electrolyte solution is prepared in advance, and a positive electrode, a negative electrode, an electrolyte membrane, and a separator as necessary are formed by bending or stacking as described above, and then the battery A non-aqueous secondary battery can also be produced by being housed in a case. The shape of the non-aqueous secondary battery of this embodiment is not particularly limited, and for example, a cylindrical shape, an elliptical shape, a rectangular tube shape, a button shape, a coin shape, a flat shape, a laminate shape, and the like are suitably employed.

The non-aqueous lithium-on secondary battery in the present embodiment can function as a battery by initial charging, but is stabilized by decomposition of a part of the electrolyte during the initial charging. Although there is no restriction | limiting in particular about the method of initial charge in this embodiment, It is preferable that initial charge is performed at 0.001-0.3C, It is more preferable to be performed at 0.002-0.25C, 0.003 More preferably, it is carried out at ~ 0.2C. In addition, it is also preferable that the initial charging is performed via the constant voltage charging in the middle. In addition, the constant current which discharges rated capacity in 1 hour is 1C. By setting the voltage range in which the lithium salt is involved in the electrochemical reaction to be long, SEI (Solid Electrolyte Interphase) is formed on the electrode surface, which has an effect of suppressing an increase in internal resistance including the positive electrode. In addition, since the reaction product is not firmly fixed only on the negative electrode, and in some form it has a good effect on other members such as the positive electrode and the separator, the electrochemical property of the lithium salt dissolved in the electrolyte It is very effective to perform the first charge in consideration of the reaction.
As mentioned above, although the form for implementing this invention was demonstrated, this invention is not limited to the said embodiment. The present invention can be variously modified without departing from the gist thereof.

EXAMPLES Hereinafter, although an Example etc. demonstrate this invention concretely, this invention is not limited to these Examples.
[Reference example]
<Preparation of constant ratio composite oxide>
A constant ratio composite oxide having a composition represented by Li _1.2 Ni _0.175 Co _0.10 Mn _0.525 O ₂ was prepared using transition metal nitrate and Li carbonate as raw materials.
NiSO ₄ · 6H ₂ O, CoSO ₄ · 7H ₂ O, and MnSO ₄ · 5H ₂ O corresponding to the above composition were dissolved in distilled water, and the nitrate concentration was 2 mol / L to obtain a sulfate aqueous solution. Separately, Na ₂ CO ₃ and NH ₄ OH were dissolved, an Na ₂ CO ₃ / NH ₄ OH aqueous solution was prepared with a Na ₂ CO ₃ concentration of 2.5 mol / L and an NH ₄ OH concentration of 1 mol / L. Next, an aqueous Na ₂ CO ₃ / NH ₄ OH solution was gradually added to the aqueous sulfate solution while stirring to obtain a metal carbonate precipitate. The metal carbonate was filtered, washed several times with distilled water, and dried at 110 ° C. for 16 hours. After drying, the mass was measured, Li ₂ CO ₃ in an amount corresponding to the above composition was mixed, mixed and stirred in a mortar, and then the first stage baking was performed at 500 ° C. for 5 hours in an air atmosphere. Next, the mixture was pulverized and mixed in a mortar, and the second stage baking was performed at 900 ° C. for 5 hours to obtain 5 g of a composite oxide. As a result of ICP (high frequency inductively coupled plasma) measurement, the obtained composite oxide was Li: Ni: Co: Mn = 1.2: 0.175: 0.10: 0.525, and it was confirmed that it had the above composition. did.

The emission spectroscopic measurement using ICP as the light source was performed as follows. The composite oxide was finely pulverized in an agate mortar, 0.05 g was taken in a Teflon (registered trademark) container, 8 mL of aqua regia was added, and the mixture was uniformly dissolved by microwave heating. Ultrapure water was added to this solution to make 100 g, which was used as an ICP measurement sample. Measurement was carried out under the following conditions using an ICP-emission spectroscopic analyzer.
Measurement conditions: For water solvent, using cyclone chamber Plasma gas (PL1): 13 (L / min)
Sheath gas (G1): 0.3 (L / min)
Nebulizer gas pressure: 3.0 (bar)
Nebulizer flow rate: 0.2 (L / min)
High frequency power: 1.0 (kW)
The quantitative value was calculated by comparing with the analytical value of a commercially available standard solution for atomic absorption analysis.

<Quantification of transition metal average valence of composite oxide and calculation of σ>
<EDTA (ethylenediaminetetraacetic acid) titration>
First, the total transition metal content ratio of the composite oxide was determined by EDTA titration. That is, 0.015 g of the composite oxide was accurately weighed, added to a 200 ml conical beaker, 10 ml of analytical grade hydrochloric acid, and subjected to ultrasonic irradiation for 20 minutes to completely dissolve the composite oxide. A stirring bar was added to the conical beaker, ion-exchanged water was added while continuing stirring, the liquid volume was adjusted to about 100 ml with a beaker scale, and 10 ml of 1M NH ₄ Cl aqueous solution was added. Neutralization was performed by slowly adding 6 ml of 28% by volume ammonia, and the pH was adjusted to around 8.0. After adding 0.2 g of MX reagent (ammonium purpurate / potassium sulfate: 1/250 weight ratio mixed powder), stirring was continued for 3 minutes to stabilize the color development. At this time, the color of the liquid became a pale yellow color. Titration was performed with a 0.01 M EDTA standard solution using a 25 ml burette, and the titration amount was determined with the end point of vivid purple color. The EDTA titration operation was performed three times, and the average value was 13.33 ml.

<Iodine reduction titration>
Next, the content ratio of the trivalent or higher transition metal was determined by iodine reduction titration. First, prior to titration of the complex oxide, a blank was measured. That is, 0.2 ml of KI saturated solution was added to a 100 ml conical beaker, 10 ml of analytical grade hydrochloric acid was added, and after 10 minutes of ultrasonic irradiation, 1 ml of starch solution (saturated starch saturated aqueous solution) was added. At this time, the color of the solution turned purple. Thereafter, titration was carried out with a 0.01 M sodium thiosulfate standard solution using a 25 ml burette, and the titration value was determined with the time point when the color of the solution became colorless as the blank value. Next, 0.015 g of composite oxide was accurately weighed and added to another 100 ml conical beaker, 0.2 ml of KI saturated solution was added, 10 ml of analytical grade hydrochloric acid was added, and KI and composite oxidation were performed by ultrasonic irradiation for 10 minutes. The product was completely dissolved.
After adding ion-exchanged water so that it might become 50 ml with a beaker scale, stirring was started and titrated with 0.01 M sodium thiosulfate standard solution using a 25 ml burette. Titration was continued until the color of the liquid changed from yellow to yellow, and 1 ml of starch solution was added when the color of the liquid became light yellow. At this time, the color of the liquid became purple, and the titration was proceeded slowly, and the time when the color of the liquid became colorless was regarded as the end point. A blank titer was subtracted from this titer to obtain a titration value. When the above-mentioned iodine reduction titration was carried out three times and the average value thereof was determined, the titration value was 20.34 ml.

σ was determined as follows from the results of ICP and titration values. As a result of ICP measurement, since this composite oxide is Li: Ni: Co: Mn = 1.2: 0.175: 0.10: 0.525, Li ₂ MnO ₃ and LiMO ₂ (M = Mn, Ni And / or Co). In this composite oxide, Mn is tetravalent, trivalent, divalent, Ni is divalent, trivalent, Co is bivalent, and trivalent. If Mn ⁴⁺ , Mn ³⁺ , Mn ²⁺ , Co ³⁺ , Co ²⁺ , Ni ³⁺ , and Ni ²⁺ are present in 0.15 g of the composite oxide, a, b, c, d, e, f, and g mol are present, respectively. In the reaction, the following reaction occurs.

<Mn ⁴⁺ >
aMn ⁴⁺ + 4aI ⁻ → aMnI ₂ + aI ₂
aI ₂ + 2aS ₂ O ₃ ²⁻ → aS ₄ O ₆ ²⁻ + 2aI ⁻

<Mn ³⁺ >
bMn ³⁺ + 3bI ⁻ → bMnI ₂ + (1/2) bI ₂
(1/2) bI ₂ + bS ₂ O ₃ ²⁻ → (1/2) bS ₄ O ₆ ²⁻ + bI ⁻

<Mn ²⁺ >
cMn ²⁺ + 2cI ⁻ → cMnI ₂
Mn ²⁺ does not react with sodium thiosulfate because it does not liberate I ₂ .

<Co ³⁺ >
dCo ³⁺ + 3dI ⁻ → dCoI ₂ + (1/2) dI ₂
(1/2) dI ₂ + dS ₂ O ₃ ²⁻ → (1/2) dS ₄ O ₆ ²⁻ + dI ⁻

<Co ²⁺ >
eCo ²⁺ + 2eI ⁻ → eCoI ₂
Co ²⁺ does not react with sodium thiosulfate because it does not liberate I ₂ .

<Ni ³⁺ >
fNi ³⁺ + 3fI ⁻ → fNiI ₂ + (1/2) fI ₂
(1/2) fI ₂ + fS ₂ O ₃ ²⁻ → (1/2) fS ₄ O ₆ ²⁻ + fI ⁻

<Ni ²⁺ >
gNi ²⁺ +2 gI ⁻ → gNiI ₂
Ni ²⁺ does not react with sodium thiosulfate because it does not liberate I ₂ .

In summary, the sodium thiosulfate titration value is (2a + b + d + f) mol, while the EDTA titration gives a titration value of (a + b + c + d + e + f + g) mol.
Therefore, transition metal average valence = 4 × a / (a + b + c + d + e + f + g) + 3 × (b + d + f) / (a + b + c + d + e + f + g) + 2 × (c + e + g) / (a + b + c + d + e + f + g + (++++++++++++++) = 2 + (iodine titration value) / (EDTA titration value)
Since the EDTA titration value was 13.33 ml and the iodine reduction titration value was 20.34 ml, the average transition metal valence was 3.53 according to the above formula.
The content ratio of Li by ICP measurement is Li / M (total amount of Ni, Co, Mn) = 1.2 / 0.8, and Li is monovalent, so that the average valence of transition metal is 3.53 _Therefore , oxygen became O _2.012 and σ was σ = −0.012.

[Example 1]
<Preparation of oxygen-deficient composite oxide>
The fixed ratio composite oxide prepared in the above reference example was placed in a magnetic dish and introduced into a horizontal tubular furnace equipped with a quartz reaction tube through which gas can flow. After introducing nitrogen into the reaction tube and confirming that oxygen was removed to 0.1% by volume or less with an oxygen concentration meter incorporated in the gas flow path, it was changed to nitrogen introduction, and the propylene concentration was changed by nitrogen. Distribution of the mixed gas diluted to 3.5% by volume was started to the reaction tube at a flow rate of 1 L / min. While continuing the flow of the mixed gas, the heating of the tubular furnace was started, the temperature was increased over 1 hour until the temperature of the introduced constant ratio composite oxide reached 450 ° C, and after reaching 450 ° C, Heating was continued while maintaining the temperature for 3 hours. After the heating was completed, the gas flow was switched to a flow of nitrogen only, and the mixture was gradually cooled to room temperature at a rate of 5 ° C./min. A sample was taken out from the reaction tube to obtain an oxygen-deficient composite oxide. When σ was determined by the same method as in the reference example, σ = 0.020.

[Example 2]
When the oxygen deficient composite oxide was prepared under the same conditions as in Example 1 except that the holding time at 450 ° C. was 5 hours, the oxygen deficient composite oxide with σ = 0.036 was obtained. .

[Example 3]
When the oxygen-deficient composite oxide was prepared under the same conditions as in Example 1 except that the nitrogen dilution concentration of propylene was 4.0% by volume, σ = 0.040 was obtained.

[Example 4]
When the oxygen-deficient composite oxide was prepared under the same conditions as in Example 1 except that the nitrogen dilution concentration of propylene was 3.0% by volume and the time maintained at 450 ° C. was 8 hours, σ = It was 0.032.

[Example 5]
When the oxygen deficient composite oxide was prepared under the same conditions as in Example 1 except that the heating temperature was 480 ° C., σ = 0.028.

[Comparative Example 1]
Prepared under the same conditions as in Example 1 except that 3.5% by volume of hydrogen diluted with nitrogen was used as the reducing gas, the heating temperature was 300 ° C., and the holding time was 6 hours. As a result, σ = 0.016 was obtained.

[Comparative Example 2]
Prepared under the same conditions as in Example 1 except that 3.5% by volume of hydrogen diluted with nitrogen was used as the reducing gas, the heating temperature was 250 ° C., and the holding time was 3 hours. As a result, σ = 0.000.

[Comparative Example 3]
When the oxygen deficient composite oxide was prepared under the same conditions as in Example 1 except that 3.5% by volume of hydrogen diluted with nitrogen was used as the reducing gas and the heating temperature was 320 ° C., σ was = 0.008.

[Comparative Example 4]
When the oxygen deficient composite oxide was prepared under the same conditions as in Example 1 except that the heating temperature was 450 ° C. and the holding time was 2 Hr, σ = 0.004.

[Comparative Example 5]
When the oxygen deficient composite oxide was prepared under the same conditions as in Example 1 except that the heating temperature was 450 ° C. and the holding time was 10 Hr, σ = 0.068.
Table 1 below shows a list of preparation conditions and σ of Examples 1 to 5 and Comparative Examples 1 to 5.

<XRD measurement of composite oxide>
XRD analysis of the prepared composite oxide was performed under the following conditions.
(Measurement conditions) Detector: Semiconductor detector, Tube: Cu, Tube voltage: 40 kV, Tube current: 40 mA, Divergence slit: 0.3 °, Step width: 0.02 ° / step, Measurement time: 3 sec
The prepared composite oxide was pulverized in a mortar and measured. A peak at 2θ = 18.6 ± 0.2 ° was used as the peak of the (003) plane, and a peak at 2θ = 44.6 ± 0.2 ° was used as the peak of the (104) plane. For each peak intensity, a perpendicular line was drawn from the peak top with a line connecting points where no peaks exist in the diffraction pattern as a base line, and the length of the line segment intersecting with the base line was defined as the intensity. The full width at half maximum was expressed in 2θ by drawing a horizontal line at the point where the line segment of the obtained intensity was divided into two equal parts and the length of the intersection with the diffraction pattern as the half width. The measurement results are shown in Table 2 below.

<Electrode production>
The electrodes were prepared as follows.
(Preparation of positive electrode)
The composite oxide prepared above was used as a positive electrode active material, and acetylene black powder having a number average particle size of 48 nm as a conductive auxiliary agent and polytetrafluoroethylene (PTFE) as a binder at a ratio of 4: 5: 1. Mixed by mass ratio. The resulting mixture was mixed with ethanol contained, stretched, and formed into a sheet. After drying, 20 mg was cut out and used as a positive electrode sheet. Next, the cut out positive electrode sheet was pressure-bonded to a 15.958 mmφ aluminum mesh at 2 tons / cm ² and vacuum-dried to obtain a positive electrode (P).
(Preparation of negative electrode)
Graphite carbon powder having a number average particle diameter of 12.7 μm and graphite carbon powder having a number average particle diameter of 6.5 μm as a negative electrode active material, a carboxymethylcellulose solution (solid content concentration 1.83% by mass) as a binder, and a diene rubber ( Glass transition temperature: −5 ° C., number average particle size upon drying: 120 nm, dispersion medium: water, solid content concentration of 40% by mass) at a solid content mass ratio of 90: 10: 1.44: 1.76 The mixture was mixed so that the total solid content concentration was 45% by mass to prepare a slurry solution. This slurry solution was applied to one side of a 10 μm thick copper foil, the solvent was removed by drying, and then rolled with a roll press to obtain a negative electrode (N). In addition, about the compound material after vacuum drying in the electrode obtained in the negative electrode (N), the amount per unit area is 5.0 mg / cm ² ± 3%, the thickness on one side is 40 μm ± 3%, and the density is 1 The slurry-like solution was prepared while adjusting the amount of solvent so that the coating width was 150 mm with respect to the width of 200 mm of the copper foil, and .25 g / cm ³ ± 3%.

<Preparation of electrolyte>
Using a solvent in which ethylmethyl carbonate (EMC) and ethylene carbonate (EC) were mixed at a volume ratio of 7: 3 as a solvent, LiPF ₆ was added as a lithium salt to a concentration of 1 mol / L, and an electrolyte solution Was prepared.

<Production of evaluation battery>
A small non-aqueous secondary battery was produced by combining the electrode obtained by the above-described method and an electrolytic solution. A specific manufacturing method is described below.
(Assembling a small non-aqueous secondary battery)
A positive electrode (P) obtained as described above and a negative electrode (N) obtained as described above are punched into a disk shape having a diameter of 16 mm, and a separator made of polyethylene (thickness 25 μm, porosity) 50% and a pore size of 0.1 μm to 1 μm) was laminated on both sides to obtain a laminate. The laminate was inserted into a SUS coin-type battery case. Next, 0.1 mL of the electrolyte solution is injected into the battery case, and the laminate is immersed in the electrolyte solution. Then, the battery case is sealed and held at 25 ° C. for 24 hours, and the electrolyte solution is sufficiently adjusted to the laminate. A small non-aqueous secondary battery was obtained.

<Evaluation>
With respect to the evaluation battery obtained as described above, the discharge capacity at a specific discharge current was measured according to the following procedure to evaluate the discharge characteristics of the nonaqueous secondary battery. The measurement was performed using a charge / discharge device ACD-01 (trade name) manufactured by Asuka Electronics Co., Ltd. and a thermostatic chamber IN-804 (trade name) manufactured by Yamato Scientific Co., Ltd. The battery was charged with a constant current of 0.2 mA (0.1 C Rate) and reached 4.7 V, and then charged with a constant voltage of 4.7 V for a total of 8 hours. The battery for evaluation using the positive electrode made of the composite oxide prepared in the reference example was discharged to 2 V at 0.2 mA (0.1 C Rate) after the charging, and the discharge capacity was determined to be 248.2 mAh / g. Next, the composite oxides prepared in Examples 1 to 5 and Comparative Examples 1 to 5 were discharged to 2.0 V at a constant current of 0.6 mA (0.3 C Rate) and 10 mA (5 C Rate) after the charging. The discharge capacity was determined. The ambient temperature of the battery at this time was set to 25 ° C.

The discharge rate characteristics were evaluated according to the following formula.
Discharge capacity ratio = [discharge capacity at 5C rate] / [discharge capacity at 0.3C rate]

  Table 2 below shows the results of XRD measurement of the composite oxides obtained in Examples 1 to 5, Comparative Examples 1 to 5, and Reference Examples, and the initial discharge capacities of batteries produced using these as positive electrode active materials. Show.

  From the results shown in Table 2, the batteries (Examples 1 to 5) using the composite oxide according to the present embodiment as the positive electrode active material had a significantly higher discharge capacity ratio than the batteries produced in Comparative Examples 1 to 5. I understand that it is expensive.

  Non-aqueous lithium ion secondary batteries obtained using the composite oxide of the present invention as a positive electrode active material include, for example, hybrid vehicles and plug-in hybrid vehicles in addition to portable devices such as mobile phones, portable audio devices, personal computers and IC tags. It can be suitably used in a rechargeable battery for an automobile such as an electric vehicle, and further in a residential power storage system.

DESCRIPTION OF SYMBOLS 100 Lithium ion secondary battery 110 Separator 120 Positive electrode 130 Negative electrode 140 Positive electrode collector 150 Negative electrode collector 160 Battery exterior

Claims (11)

The following general formula:
Li [Li _X Ni _a Mn _b Co _c ] O _2-σ
{Where x + a + b + c = 1, 0.1 <x <0.25, 0 <a <0.3, 0 <b <0.65, 0 <c <0.3, and 0.01 <σ <0 .05. } And the crystal plane diffraction intensities of the (003) plane and (104) plane in X-ray diffraction measurement are I (003) and I (104), respectively, 1.6 <I (003) / A composite oxide for a positive electrode active material of a non-aqueous lithium ion battery having a layered structure characterized by I (104) <4.0. 2. The positive electrode active material for a non-aqueous lithium ion battery according to claim 1, wherein when the half width of the (003) plane is H (003), 0.08 ° <H (003) <0.13 °. use complex oxide. The positive electrode active material for a non-aqueous lithium ion battery according to claim 1 or 2, wherein 0.15 <a <0.2, 0.4 <b <0.55, and 0.05 <c <0.2. use complex oxide. The composite oxide for a positive electrode active material for a non-aqueous lithium ion battery according to claim 1, wherein 0.015 <σ <0.04. 5. The composite oxide for a positive electrode active material of a non-aqueous lithium ion battery according to claim 1, wherein 1.8 <I (003) / I (104) <2.5. below:
The following general formula:
Li [Li _x Ni _a Mn _b Co _c ] O _2-σ
{Where x + a + b + c = 1, 0.1 <x <0.25, 0 <a <0.3, 0 <b <0.65, 0 <c <0.3, and −0.04 <σ ≦ 0.01. A step of reducing a composite oxide having a layered structure represented by
The manufacturing method of the composite oxide for positive electrode active materials of the non-aqueous lithium ion battery of any one of Claims 1-5 characterized by the above - mentioned. The method for producing a composite oxide for a positive electrode active material of a non-aqueous lithium ion battery according to claim 6, wherein the hydrocarbon is a hydrocarbon having 1 to 5 carbon atoms. The method for producing a composite oxide for a positive electrode active material of a non-aqueous lithium ion battery according to claim 7, wherein the hydrocarbon is at least one selected from the group consisting of methane, ethane, ethylene, propane, propylene, and butane. . The method for producing a composite oxide for a positive electrode active material of a non-aqueous lithium ion battery according to claim 8, wherein the hydrocarbon is propylene. The composite oxide for a positive electrode active material of a non-aqueous lithium ion battery according to any one of claims 1 to 5 or the positive electrode active material of a non-aqueous lithium ion battery according to any one of claims 6 to 9 . the positive electrode active material containing a positive electrode active material for a composite oxide of a non-aqueous lithium ion battery manufactured by the manufacturing method of the composite oxide.   A non-aqueous lithium ion secondary battery comprising the positive electrode active material according to claim 10.

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