JP2002203540A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery superior in high temperature storage characteristics and load characteristics. SOLUTION: In the nonaqueous electrolyte secondary battery equipped with a positive electrode having a positive electrode mixture layer composed of manganese containing oxide and nickel containing oxide as the main body, with a negative electrode comprised by containing at least one kind among lithium metal, lithium alloy or a material capable of doping/de-doping lithium, and with the nonaqueous electrolyte, Li2CO3 is contained in the positive electrode mixture layer, and the content of the Li2CO3 is in the range larger than 0 wt.% and not more than 5 wt.% in the positive electrode mixture layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to lithium (Li)
The present invention relates to a non-aqueous electrolyte secondary battery including a positive electrode including a manganese-containing oxide containing manganese and manganese (Mn) and a nickel-containing oxide containing lithium and nickel (Ni).

[0002]

2. Description of the Related Art In recent years, with the advance of electronic technology, many small portable electronic devices such as a camera-integrated VTR (video tape recorder), a mobile phone and a laptop computer have become widespread. Have been. Therefore, as a portable power supply used for them, a battery that is small and lightweight and has a high energy density,
In particular, the development of secondary batteries is underway. Above all, lithium ion secondary batteries using a non-aqueous electrolyte are greatly expected because they can obtain higher energy density than lead batteries or nickel-cadmium batteries.

As the positive electrode material of this lithium ion secondary battery, lithium-cobalt composite oxide, lithium-manganese composite oxide, lithium-nickel composite oxide and the like have been put to practical use. Among these, the lithium-cobalt composite oxide has the best balance in various aspects such as battery capacity, cost, and thermal stability, and is currently widely used. In contrast, lithium-manganese composite oxides have drawbacks such as low battery capacity and slightly poor high-temperature storage characteristics, while lithium-nickel composite oxides have drawbacks such as slightly lower thermal stability. These are excellent in terms of raw material price and stable supply, and research is being conducted for future utilization. For example, recently, by mixing and using a lithium-manganese composite oxide and a lithium-nickel composite oxide, the disadvantages of both are complemented, and expansion and contraction of the positive electrode during charging and discharging are suppressed, and the charge-discharge cycle is reduced. A technique for improving characteristics has been proposed (see Japanese Patent Application Laid-Open No. 8-45498).

[0004]

However, in the secondary battery disclosed in Japanese Patent Application Laid-Open No. Hei 8-45498,
For example, when stored in a high-temperature environment of 45 ° C. to 60 ° C., there is a problem that characteristics are deteriorated. In particular, when used in information terminals such as mobile phones, high load (high current density) and high end voltage capacity are required.
Sufficient values could not be obtained after high-temperature storage. Further, in the secondary electric field, there is a problem that the charge / discharge cycle characteristics cannot be sufficiently improved depending on the particle diameters of the lithium-manganese composite oxide and the lithium-nickel composite oxide.

Accordingly, the present invention has been proposed for the purpose of providing a secondary battery having excellent high-temperature storage characteristics and also excellent load characteristics.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides lithium (Li) and manganese (Mn).
And at least one first element selected from the group consisting of metal elements other than manganese and boron (B), and oxygen (O), and the molar ratio of the first element to manganese (first Element / manganese) is 0.01 / 1.
A manganese-containing oxide in the range of 99 or more and 0.5 / 1.5 or less, lithium, nickel (Ni), and at least one second element selected from the group consisting of metal elements other than nickel and boron; Nickel containing an element and oxygen, wherein the molar ratio of the second element to the nickel (second element / nickel) is in the range of 0.01 / 0.99 to 0.5 / 0.5. Positive electrode comprising a positive electrode mixture layer mainly containing oxides, lithium metal, lithium alloy,
Alternatively, in a non-aqueous electrolyte secondary battery including a negative electrode containing at least one or more materials capable of doping / dedoping lithium and a non-aqueous electrolyte, Li ₂ CO
₃ is contained in the positive electrode mixture layer, and the content of Li ₂ CO _{3 in} the positive electrode mixture layer is more than 0% by weight and 5% by weight or less.

[0007] The non-aqueous electrolyte secondary battery according to the present invention configured as described above has excellent high-temperature storage characteristics because Li ₂ CO ₃ is contained in the positive electrode mixture layer at a content within the above range. And excellent load characteristics.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a cross-sectional structure of a non-aqueous electrolyte secondary battery according to one embodiment of the present invention. This non-aqueous electrolyte secondary battery is a so-called cylindrical type, and has a band-shaped positive electrode 11 and a negative electrode 12 inside a substantially hollow cylindrical battery can 1.
Electrode body 10 wound with a separator 13
have. The battery can 1 is made of, for example, iron (Fe) plated with nickel, and has one end closed and the other end open. Inside the battery can 1,
A pair of insulating plates 2 and 3 are arranged perpendicular to the winding peripheral surface so as to sandwich the winding electrode body 10.

At the open end of the battery can 1, a battery cover 4, a safety valve mechanism 5 provided inside the battery cover 4, and a positive temperature coefficient (PTC) element are provided.
Element 6 is attached by caulking via a gasket 7, and the inside of the battery can 1 is sealed. The battery lid 4 is made of, for example, the same material as the battery can 1. The safety valve mechanism 5 includes a thermal resistance element 6
When the internal pressure of the battery becomes higher than a certain level due to an internal short circuit or external heating, the disk plate 5a is inverted and the battery lid 4 and the wound electrode body are electrically connected to each other. The electrical connection with 10 is cut off. The heat sensitive resistance element 6 limits the current by increasing the resistance value when the temperature rises, and prevents abnormal heat generation due to a large current, and is made of, for example, barium titanate-based semiconductor ceramics. The gasket 7 is made of, for example, an insulating material, and its surface is coated with asphalt.

The wound electrode body 10 includes, for example, a center pin 1
It is wound around 4. A positive electrode lead 15 made of aluminum (Al) or the like is connected to the positive electrode 11 of the wound electrode body 10, and a negative electrode lead 16 made of nickel or the like is connected to the negative electrode 12. The positive electrode lead 15 is welded to the safety valve mechanism 5 so that the battery cover 4
The negative electrode lead 16 is electrically connected to the battery can 1 by welding.

The positive electrode 11 includes, for example, a positive electrode mixture layer and a positive electrode current collector layer, and has a structure in which a positive electrode mixture layer is provided on both surfaces or one surface of the positive electrode current collector layer. . The positive electrode current collector layer is made of, for example, a metal foil such as an aluminum foil, a nickel foil, or a stainless steel foil.

The positive electrode mixture layer contains a manganese-containing oxide and a nickel-containing oxide as described below as a positive electrode active material. If necessary, a conductive material such as graphite and a polyvinylidene fluoride or the like may be further used. Contains a binder.

The positive electrode mixture layer contains Li ₂ CO 3
₃ is contained. When the content of Li ₂ CO ₃ is more than 0% by weight in the positive electrode mixture layer,
% By weight or less.

If the positive electrode mixture layer does not contain Li ₂ CO ₃ , the high-temperature storage characteristics are not improved. On the other hand, if the content of Li ₂ CO ₃ in the positive electrode mixture layer exceeds 5% by weight, the proportion of Li ₂ CO ₃ that does not contribute to electron conduction occupies a large amount, so that the conductivity of the positive electrode decreases and the load characteristics decrease. I do.

Therefore, in a non-aqueous electrolyte secondary battery, L
i ₂ CO ₃ is contained in the positive electrode mixture layer, and the Li ₂ CO 3
_When the content of No. ₃ is in the range of more than 0% by weight and not more than 5% by weight in the positive electrode mixture layer, the high-temperature storage characteristics and the load characteristics are excellent.

The manganese-containing oxide contains lithium, manganese, at least one first element selected from the group consisting of metal elements other than manganese and boron, and oxygen. The manganese-containing oxide has, for example, a cubic (spinel) structure or a tetragonal structure, and the first element is present at a part of the site of the manganese atom by being replaced with the manganese atom. Formula manganese-containing oxide, expressed the first element in _{Ma Li x Mn 2-y Ma} y
Represented by the O _4. Here, the value of x is in the range of 0.9 ≦ x ≦ 2, and the value of y is in the range of 0.01 ≦ y ≦ 0.5. That is, the composition ratio of the first element to manganese, Ma / Mn, is not less than 0.01 / 1.99 and not more than 0.1 in terms of molar ratio.
The range is 5 / 1.5 or less.

As the first element, specifically, iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), aluminum (Al), tin (Sn) , Chromium (Cr), vanadium (V), titanium (Ti), magnesium (Mg), calcium (C
a), strontium (Sr), boron (B), gallium (Ga), indium (In), silicon (Si), and germanium (Ge) are preferred. Manganese-containing oxides containing these as the first element can be obtained relatively easily and are chemically stable.

Nickel-containing oxides include lithium and nickel.
Group consisting of Kel, metal elements other than nickel, and boron
At least one second element selected from the group consisting of
Contains. This nickel-containing oxide has, for example, a layered structure.
And the second element is a nickel atom site
Is present by being replaced with a nickel atom. Ni
The chemical formula of the Kel-containing oxide represents the second element by Mb
And typically LiNi _1-zMb_zO₂Indicated by
The composition ratio of lithium and oxygen is Li: O = 1: 2.
The value of z may be within the range of 0.01 ≦ z ≦ 0.5
It is. That is, the composition of the second element with respect to nickel
The ratio Mb / Ni is 0.01 / 0.99 or more in a molar ratio of 0.1 to 0.9.
It is within the range of 5 / 0.5 or less.

As the second element, iron, cobalt,
At least one selected from the group consisting of manganese, copper, zinc, aluminum, tin, chromium, vanadium, titanium, magnesium, calcium, strontium, boron, gallium, indium, silicon and germanium is preferred. This is because nickel-containing oxides containing these as the second element can be obtained relatively easily and are chemically stable.

These manganese-containing oxides and nickel-containing oxides are considered to stabilize the crystal structure by replacing a part of manganese or nickel with the other elements described above. In a secondary battery, high-temperature storage characteristics can be improved. Composition ratio of first element to manganese Ma / M
n is 0.01 / 1.99 or more and 0.5 / 1.5 or less in molar ratio, and the composition ratio Mb / N of the second element with respect to nickel.
The reason why the molar ratio i is 0.01 / 0.99 or more and 0.5 / 0.5 or less is that if the substitution amount is less than this, a sufficient effect cannot be obtained, and the substitution amount is more than this. If the amount is too large, the high-load discharge capacity after high-temperature storage decreases.

The mixing ratio of the manganese-containing oxide and the nickel-containing oxide in the positive electrode 11 is, by mass ratio, 10 to 80 of the manganese-containing oxide and 90 to 90 of the nickel-containing oxide.
It is preferably 20. Since the manganese-containing oxide is significantly deteriorated in the electrolyte described later in a high-temperature atmosphere, if the content of the manganese-containing oxide is larger than this, the internal resistance increases after high-temperature storage, and the capacity decreases. It is because. Further, since the nickel-containing oxide has a low discharge potential, if the content of the nickel-containing oxide is larger than this, the high-load discharge capacity at a high-potential cutoff after high-temperature storage becomes low. .

The average particle diameter of the manganese-containing oxide and the nickel-containing oxide is preferably 30 μm or less. If the average particle diameter is larger than this, expansion and contraction of the positive electrode 11 due to charge and discharge cannot be sufficiently suppressed, and sufficient charge and discharge cycle characteristics cannot be obtained at room temperature.

As the manganese-containing oxide and the nickel-containing oxide, for example, a compound containing a lithium compound, a manganese compound and a first element, or a compound containing a lithium compound, a nickel compound and a second element are prepared. After mixing them at a desired ratio, they can be obtained by heating and firing at a temperature of 600 ° C. to 1000 ° C. in an atmosphere containing oxygen. At that time, as a compound of a raw material, a carbonate, a hydroxide, an oxide, a nitrate, an organic acid salt or the like is used.

The negative electrode 12 is, for example, similar to the positive electrode 11,
The negative electrode current collector layer has a structure in which negative electrode mixture layers are respectively provided on both surfaces or one surface. The negative electrode current collector layer is made of, for example, a metal foil such as a copper foil, a nickel foil, and a stainless steel foil. The negative electrode mixture layer is, for example, lithium metal, or capable of absorbing and releasing lithium at a potential of, for example, 2 V or less on the basis of the lithium metal potential, that is, any one of a dope / dedopable negative electrode material or It contains two or more kinds, and further contains a binder such as polyvinylidene fluoride as needed.

Examples of the negative electrode material capable of doping and undoping lithium include lithium metal and lithium alloy compounds. The lithium alloy compound here, for example, those represented by the chemical formula D _s E _t Li _u. In this chemical formula, D represents at least one of a metal element and a semiconductor element capable of forming an alloy or a compound with lithium, and E represents at least one of a metal element and a semiconductor element other than lithium and D. The values of s, t, and u are s> 0, t ≧ 0, and u ≧ 0, respectively.

Here, as a metal element or a semiconductor element capable of forming an alloy or a compound with lithium, 4B
Group metal elements or semiconductor elements are preferred, particularly preferably silicon or tin, and most preferably silicon. Examples of metals or semiconductors that can form alloys or compounds with lithium include Mg, B, Al, and G.
a, In, Si, Ge, Sn, Pb, Sb, Bi, C
d, Ag, Zn, Hf, Zr, Y and their alloy compounds, for example, Li-Al, Li-Al-M (wherein,
M is composed of one or more of 2A, 3B and 4B transition metal elements. ) AlSb, CuMgSb and the like. In addition, these alloys or compounds are also preferable. For example, M _x Si (where M is one or more metal elements excluding Si and x is 0 <x) or M _x Sn (where
M is one or more metal elements except Sn, and x is 0 <
x. ). Specifically, SiB ₄ , S
iB ₆ , Mg ₂ Si, Mg ₂ Sn, Ni ₂ Si, TiS
i ₂ , MoSi ₂ , CoSi ₂ , NiSi ₂ , CaSi
_{2, CrSi 2, Cu 5 Si} , FeSi 2, MnS
_{i 2, NbSi 2, TaSi 2} , VSi 2, such as WSi ₂ or ZnSi ₂ and the like.

Further, as the anode material, the above-mentioned elements or compounds which can be alloyed or compounded with lithium can also be used. That is, in this material,
One or more kinds of group 4B elements may be contained, and metal elements other than group 4B containing lithium may be contained.
Such materials include SiC, Si ₃ N ₄ , Si ₂
N ₂ O, Ge ₂ N ₂ O, SiO _x (where x is 0 <x ≦
2. ), SnO _x (where x is 0 <x ≦ 2), LiSiO, LiSnO and the like.

Examples of the anode material capable of doping / dedoping lithium include carbon materials, metal oxides, and polymer materials. As a carbon material, for example,
Examples include non-graphitizable carbon, artificial graphite, cokes, graphites, glassy carbons, fired organic polymer compounds, carbon fibers, activated carbon, and carbon blacks. Among them, cokes include pitch coke, needle coke, petroleum coke, etc. An organic polymer compound fired body is obtained by firing a polymer material such as phenol resin or furan resin at an appropriate temperature to carbonize. Means what you do. Examples of the metal oxide include iron oxide, ruthenium oxide, molybdenum oxide and tin oxide, and examples of the polymer material include polyacetylene and polypyrrole.

The separator 13 is made of, for example, a porous film made of a polyolefin-based material such as polypropylene or polyethylene, or a porous film made of an inorganic material such as a ceramic nonwoven fabric. It may have a structure in which porous films are stacked.

The separator 13 is impregnated with a non-aqueous electrolyte which is a liquid non-aqueous electrolyte. The non-aqueous electrolyte is a non-aqueous solvent in which, for example, a lithium salt is dissolved as an electrolyte salt. Examples of the non-aqueous solvent include propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyllactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3 -Dioxolan, 4-methyl-1,3-dioxolan, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitrile, anisole, acetate, butyrate or propionate, and the like.
Seeds or a mixture of two or more kinds are used.

As the lithium salt, for example, LiCl
O ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiB
(C ₆ H ₅ ), LiCH ₃ SO ₃ , LiCF ₃ SO ₃ ,
There are LiCl, LiBr, and the like, and one or more of these are used in combination.

The non-aqueous electrolyte secondary battery configured as described above, includes a positive electrode mixture layer is _Li 2 CO ₃ is contained, the content of _Li 2 CO ₃ in the positive electrode mixture layer is 0 weight % And 5% by weight or less, it is excellent in high-temperature storage characteristics and load characteristics.

This non-aqueous electrolyte secondary battery can be manufactured, for example, as follows.

First, a positive electrode mixture is prepared by mixing a manganese-containing oxide and a nickel-containing oxide as the positive electrode active material, and if necessary, a conductive agent and a binder. Next, this positive electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone to obtain a paste-like positive electrode mixture slurry. The positive electrode mixture slurry is applied to the positive electrode current collector layer, the solvent is dried, and then compression molded by a roller press or the like to form a positive electrode mixture layer, and the positive electrode 11 is manufactured.

In this positive electrode mixture layer, Li ₂ CO ₃ contains 0
It is contained in a range of more than 5% by weight and less than 5% by weight. The content of Li ₂ CO ₃ in the positive electrode mixture layer is adjusted to the above range by appropriately adjusting the amount of Li ₂ CO ₃ added when preparing the positive electrode mixture.

By the way, Li ₂ CO ₃ is sometimes used as one kind of raw material for synthesizing a manganese-containing oxide.
When Li ₂ CO ₃ is used as one of the raw materials for synthesizing a manganese-containing oxide, Li ₂ CO ₃ may remain in the manganese-containing oxide even after the synthesis. Thus, using the positive electrode active material in which Li ₂ CO ₃ remains,
The content of Li ₂ CO ₃ in the positive electrode mixture layer may be greater than 0% by weight and 5% by weight or less.

After the synthesis of the manganese-containing oxide, Li ₂ CO ₃ remaining in the positive electrode active material due to non-reaction was obtained.
If the residual amount of Li ₂ C is large, the Li ₂ C remaining in the positive electrode active material
What is necessary is just to mix suitably with a thing with a small residual amount of O ₃ , and finally make the content of Li ₂ CO ₃ contained in the positive electrode mixture layer into the above range.

Next, a negative electrode mixture was prepared by mixing the negative electrode active material and, if necessary, a binder.
Dispersed in a solvent such as methyl-2-pyrrolidone to obtain a paste-like negative electrode mixture slurry. After applying this negative electrode mixture slurry to the negative electrode current collector layer and drying the solvent, compression molding is performed by a roller press or the like to form a negative electrode mixture layer,
The negative electrode 12 is manufactured.

Subsequently, the positive electrode lead 15 is attached to the positive electrode current collector layer by welding or the like, and the negative electrode lead 16 is attached to the negative electrode current collector layer by welding or the like. Thereafter, the positive electrode 11 and the negative electrode 12 are wound via the separator 13,
The distal end of the positive electrode lead 15 was welded to the safety valve mechanism 5 and the distal end of the negative electrode lead 16 was welded to the battery can 1.
The wound positive electrode 11 and negative electrode 12 are sandwiched between a pair of insulating plates 2 and 3 and housed inside the battery can 1. Positive electrode 11 and negative electrode 12
Is stored in the battery can 1 and then a non-aqueous electrolyte is injected into the battery can 1 and impregnated in the separator 13.

Thereafter, the battery lid 4 is attached to the open end of the battery can 1.
The safety valve mechanism 5 and the thermal resistance element 6 are fixed by caulking via the gasket 7. Thus, the non-aqueous electrolyte secondary battery shown in FIG. 1 is formed.

It should be noted that the present invention is not limited to the above description, and can be appropriately modified without departing from the gist of the present invention.

Therefore, in the above description, an example of a cylindrical non-aqueous electrolyte secondary battery having a wound structure has been specifically described, but the present invention is not limited to this. The present invention can also be applied to a secondary battery. Also, the shape of the battery is not limited to a cylindrical shape, and non-cylindrical non-cylindrical batteries having various shapes such as a coin type, a button type, a square type, or a type in which an electrode element is sealed inside a laminated film other than the cylindrical type. The same can be applied to a water electrolyte secondary battery.

In the above description, the case where a non-aqueous electrolyte obtained by dissolving an electrolyte salt in a non-aqueous solvent is used as an example of the non-aqueous electrolyte has been described, but the present invention is not limited to this. Rather, as a non-aqueous electrolyte, a gel electrolyte composed of an electrolyte salt, a swelling solvent, and a matrix polymer, a solid polymer electrolyte composed of an ion conductive polymer and an electrolyte salt, an ion conductive inorganic ceramic, glass Also, the present invention can be applied to a case where a non-aqueous electrolyte material or the like obtained by mixing an inorganic solid electrolyte mainly containing ionic crystals or the like and a non-aqueous electrolyte is used.

For example, when a gel electrolyte is used as the non-aqueous electrolyte, the composition of the gel electrolyte and the structure of the matrix polymer constituting the gel electrolyte are not limited as long as the ionic conductivity of the gel electrolyte is 1 mS / cm or more. No problem.

Specific matrix polymers include polyacrylonitrile, polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and polyhexafluoropropylene, polytetrafluoroethylene, polyhexafluoropropylene, polyethylene oxide, polypropylene oxide, and polyphophate. Sphazen, polysiloxane, polyvinyl acetate, polyvinyl alcohol, polymethyl methacrylate, polyacrylic acid, polymethacrylic acid, styrene-butadiene rubber, nitrile-butadiene rubber, polystyrene, polycarbonate, and the like can be used. In particular, in consideration of electrochemical stability, it is preferable to use polyacrylonitrile, polyvinylidene fluoride, polyhexafluoropropylene, polyethylene oxide, or the like.

Although the weight of the matrix polymer required for preparing the gel electrolyte is different depending on the compatibility between the matrix polymer and the non-aqueous electrolyte, it is difficult to unconditionally define it. 5% by weight to 50% of electrolyte
It is preferable to set the weight%.

[0048]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on specific experimental results.

Example 1 [Preparation of Positive Electrode] First, lithium carbonate (Li ₂ CO ₃ ), manganese dioxide (MnO ₂ ), and nichrome trioxide (CrO 3)
₃ ) and fired in air at 850 ° C. for 5 hours to produce a manganese-containing oxide containing lithium, manganese, and chromium as the first element (Ma).

Further, lithium hydroxide (LiOH), nickel monoxide (NiO), and cobalt monoxide (CoO) are mixed, and calcined in air at a temperature of 750 ° C. for 5 hours, so that lithium, nickel and the second A nickel-containing oxide containing cobalt as an element (Mb) was produced.

Next, the obtained manganese-containing oxide and nickel-containing oxide were each pulverized and then mixed at a weight ratio of 50:50 to obtain a positive electrode active material.

Further, Li ₂ C contained in the positive electrode active material
The content of O ₃ was 0.01% by weight. The measurement of the content of Li ₂ CO ₃ contained in the positive electrode active material was performed by
This was performed as shown below.

First, the positive electrode active material sample was decomposed with sulfuric acid to generate CO ₂ . Was then absorb this CO ₂ in a solution of sodium hydroxide and barium chloride. Then, this solution was titrated with an acid standard solution to quantify CO ₂ . Then, the content of Li ₂ CO ₂ contained in the positive electrode active material was determined by converting from the amount of CO ₂ .

Next, 6 parts by weight of graphite as a conductive agent and 3 parts by weight of poly (vinylidene fluoride) as a binder were mixed with 91 parts by weight of the positive electrode active material to prepare a positive electrode mixture. Then, this positive electrode mixture was dried and formed into a disk shape having a diameter of 15.5 mm, thereby obtaining a pellet-shaped positive electrode.

[Production of Negative Electrode] First, 30 parts by weight of coal tar pitch as a binder was added to 100 parts by weight of coal-based coke as a filler, mixed at about 100 ° C., and compression-molded with a press machine. A carbon molded body was produced by heat treatment at a temperature of not more than ℃. Subsequently, the carbon molded body is impregnated with a coal tar pitch melted at a temperature of 200 ° C. or less, and a heat treatment is performed at a temperature of 1000 ° C. or less. Heat treatment was performed to produce a graphitized molded body. Thereafter, the graphitized molded product was pulverized and classified to obtain a powder.

The obtained graphitized powder was subjected to a structural analysis by an X-ray diffraction method. As a result, the (002) plane spacing was 0.337 nm, and the (002) plane C-axis crystallite thickness was 50. It was 0 nm. The true density determined by the pycnometer method is 2.23 g / cm ³ , the bulk density is 0.83 g / cm ³ , and the average shape parameter is 10
Met. In addition, BET (Brunauer, Emmett, Telle
The specific surface area determined by the r) method is 4.4 m ² / g,
The particle size distribution obtained by the laser diffraction method is as follows.
1.2 μm, cumulative 10% particle size is 12.3 μm, cumulative 50
% Particle size is 29.5 μm, cumulative 90% particle size is 53.7 μm
Met. In addition, the breaking strength of the graphitized particles determined using a Shimadzu micro compression tester (manufactured by Shimadzu Corporation) was 7.0 × 10 ⁷ Pa on average.

Next, 35 parts by weight of the above graphitized powder and 55 parts by weight of Mg ₂ Si powder as the negative electrode active material were mixed with 10 parts by weight of polyvinylidene fluoride as a binder to prepare a negative electrode mixture. Was dispersed in N-methylpyrrolidone to obtain a negative electrode mixture slurry. Then, the negative electrode mixture slurry is uniformly applied to both surfaces of a negative electrode current collector layer made of a strip-shaped copper foil having a thickness of 10 μm, dried, and compression molded with a roll press to form a negative electrode mixture layer. A negative electrode was prepared by punching out a disk having a diameter of 16 mm.

[Preparation of Non-Aqueous Electrolyte] Propylene Carbonate 50
A non-aqueous electrolyte was prepared by dissolving LiPF ₆ as an electrolyte salt at a ratio of 1.0 mol / l in a mixed solvent of 50% by volume of diethyl carbonate and 50% by volume of diethyl carbonate.

Using the positive electrode, the negative electrode, and the non-aqueous electrolyte prepared as described above, a coin-type non-aqueous electrolyte secondary battery was prepared as follows.

First, the negative electrode was accommodated in a negative electrode can made of stainless steel, and a nonaqueous electrolytic solution was injected into the negative electrode can. Then, a separator made of microporous polypropylene and having a thickness of 50 μm was disposed on the negative electrode. Then, after arranging the positive electrode on the separator and injecting the non-aqueous electrolyte, the positive electrode can having a three-layer structure made of aluminum, stainless steel and nickel is caulked and fixed to the negative electrode can via a polypropylene sealing gasket. As a result, a coin-type non-aqueous electrolyte secondary battery having an outer diameter of 20 mm and a height of 1.6 mm was obtained.

[0061]Examples 2 and 3 and Comparative Examples 1 to 3 Li in the positive electrode mixture layer₂CO₃The content of
Same as Example 1 except that it is as shown in Table 1
Thus, a non-aqueous electrolyte secondary battery was manufactured. Note that Li ₂CO
₃By post-addition of Li₂CO₃Content rate
I controlled.

With respect to the non-aqueous electrolyte secondary batteries of Examples 1 to 3 and Comparative Examples 1 to 3 manufactured as described above, first, a constant current of 1 mA was applied until the battery voltage reached 4.2 V. After performing constant-current constant-voltage charging, a charge-discharge cycle was performed in which constant current was discharged at a constant current of 1 mA to a cutoff voltage (cutoff voltage) of 2.5 V, and the initial discharge capacity was measured.

Next, in order to evaluate high-temperature storage characteristics and load characteristics, the following charge / discharge tests were performed.

<Evaluation of High-Temperature Storage Characteristics> After the measurement of the initial discharge capacity, the above-described charge / discharge cycle was performed again. Then, it was stored in a 60 ° C. oven for 2 weeks. Then 23
After the battery was once discharged to a final voltage of 2.5 V in an environment of ° C., 10 charge / discharge cycles were performed to measure the discharge capacity. Then, among the obtained discharge capacity values, the highest value was set as the recovery capacity, and the ratio of the recovery capacity to the initial discharge capacity was calculated as a percentage, and was set as the recovery capacity retention rate.

<Evaluation of Load Characteristics> After the battery was charged at a constant current of 1 mA until the battery voltage reached 4.2 V, 0.1 C was applied.
And the discharge capacity at 3C was measured. And 3 for 0.1 C discharge capacity
The capacity ratio (%) of the C discharge capacity was determined, and the load characteristics were evaluated based on the capacity ratio.

Table 1 shows the above measurement results together with the content of Li ₂ CO ₃ in the positive electrode mixture layer.

[0067]

[Table 1] Table 1 shows that the nonaqueous electrolyte secondary batteries of Examples 1 to 3 are excellent in high-temperature storage characteristics and load characteristics. In addition, it can be seen that the higher the content of Li ₂ CO ₃ in the positive electrode mixture layer, the better the high-temperature storage characteristics.

However, when the content of Li ₂ CO ₃ is 5
In the case of the non-aqueous electrolyte secondary batteries of Comparative Example 2 and Comparative Example 3 which exceed the weight%, L which does not contribute to electron conduction in the positive electrode mixture layer.
It can be seen that since i ₂ CO ₃ is excessively contained, the conductivity of the positive electrode decreases and the load characteristics decrease.

The non-aqueous electrolyte secondary battery of Comparative Example 1, in which the content of Li ₂ CO ₃ is 0% by weight, is poor in high-temperature storage characteristics, and is therefore not preferable for practical use.

From the above results, at least one of a positive electrode provided with a positive electrode mixture layer mainly composed of a manganese-containing oxide and a nickel-containing oxide, and at least one of lithium metal, a lithium alloy, and a material capable of doping and undoping lithium. A non-aqueous electrolyte secondary battery including a non-aqueous electrolyte including a negative electrode containing at least one type thereof has Li ₂ CO 3 in the positive electrode mixture layer.
_{3 and the} content of Li ₂ CO ₃ is 0% by weight.
It was found that when the ratio was larger than 5% by weight, the high-temperature storage characteristics were excellent and the load characteristics were excellent.

[0071]

As is apparent from the above description, the present invention
The non-aqueous electrolyte secondary battery according to
Manganese (Mn), metal elements other than manganese, and boron
(B) at least one first member selected from the group consisting of:
Element and oxygen (O), and
The molar ratio of the first element (first element / manganese) is
Within the range of 0.01 / 1.99 or more and 0.5 / 1.5 or less
Certain manganese-containing oxides, lithium and nickel (N
i) a group consisting of a metal element other than nickel and boron
At least one second element selected from the group consisting of
The molar ratio of the second element to the nickel
(Second element / nickel) is 0.01 / 0.99 or more
Nickel-containing oxide in the range of 0.5 / 0.5 or less
A positive electrode having a positive electrode mixture layer mainly composed of
Metal, lithium alloy, or lithium
Not contain at least one of the possible materials
Non-aqueous electrolyte secondary battery comprising a negative electrode and a non-aqueous electrolyte
In the positive electrode mixture layer, Li₂CO ₃Is contained
Li₂CO₃Content is 0 times in the positive electrode mixture layer.
It is in the range of more than 5% by weight. I
Therefore, according to the present invention, high-temperature storage characteristics and load characteristics
A non-aqueous electrolyte battery having excellent performance is realized.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a configuration example of a nonaqueous electrolyte secondary battery to which the present invention is applied.

[Explanation of symbols]

1 battery can, 2, 3 insulating plate, 4 battery lid, 5 safety valve mechanism, 6 thermal resistance element, 7 gasket, 10 wound electrode body, 11 positive electrode, 12 negative electrode, 13 separator,
14 Center pin, 15 Positive lead, 16 Negative lead

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshikatsu Yamamoto 2nd Hinoguchi, Motomiya-cho, Adachi-gun, Fukushima Prefecture F-term in Fukushima Co., Ltd. 5H029 AJ02 AJ04 AK03 AL06 AL12 AM03 AM05 AM07 BJ03 BJ14 HJ01 HJ02 5H050 AA02 AA10 BA17 CA09 CB07 EA01 HA01 HA02

Claims (2)

[Claims] 1. Lithium (Li) and manganese (Mn)
And at least one first element selected from the group consisting of metal elements other than manganese and boron (B), and oxygen (O), and the molar ratio of the first element to manganese (first Element / manganese) is 0.01 / 1.
A manganese-containing oxide in the range of 99 or more and 0.5 / 1.5 or less; lithium; nickel (Ni); and at least one second element selected from the group consisting of metal elements other than nickel and boron. Nickel containing an element and oxygen, wherein the molar ratio of the second element to the nickel (second element / nickel) is in the range of 0.01 / 0.99 to 0.5 / 0.5. A positive electrode including a positive electrode mixture layer mainly containing an oxide; a negative electrode including at least one of lithium metal, a lithium alloy, and a material capable of doping and undoping lithium; and a non-aqueous electrolyte. In a non-aqueous electrolyte secondary battery comprising
₂ CO ₃ is contained in the positive electrode mixture layer, and the Li ₂ C
A non-aqueous electrolyte secondary battery, wherein the content of O ₃ is in the range of more than 0% by weight and 5% by weight or less in the positive electrode mixture layer. 2. A mixing ratio of the manganese-containing oxide and the nickel-containing oxide in the positive electrode, by mass ratio,
The non-aqueous electrolyte secondary battery according to claim 1, wherein the nickel-containing oxide is 90 to 20 with respect to the manganese-containing oxide 10 to 80.