JPH0729603A - Non-aqueous electrolyte secondary battery - Google Patents

Abstract

PURPOSE:To provide a non-aqueous electrolyte secondary battery using a novel active material, where an electric charging/discharging characteristic and a cycle characteristic are improved. CONSTITUTION:A lithium ion type non-aqueous electrolyte secondary battery is composed of a positive electrode, which uses composite oxide expressed by a formula: LixMyGezOp (wherein M represents one or more kinds of a transition metal element selected from Co, Mn and Ni, 0.9<=x<=1.3, 0.8<=y<=2.0, 0.01<=z<=0.2, and 2.0<=p<=4.5) as an active material, a negative electrode, and a non-aqueous electrolyte.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium ion non-aqueous secondary battery having improved discharge performance and charge / discharge cycle performance.

[0002]

2. Description of the Related Art Non-aqueous electrolyte type secondary batteries, which use a light metal alloy containing lithium or a material that absorbs and releases lithium ions as a negative electrode active material, are actively used due to their practical advantages of high voltage and high energy density. Being researched. As the positive electrode active material of these secondary batteries, LiMn ₂ O ₄ as a layered compound utilizing intercalation of Li,
Li ₂ MnO ₃ , LiCoO ₂ , LiCo _0.5 Ni _0.5
O ₂ , LiNiO ₂ , MoS _2, etc. have been commonly used. Among these, LiCoO ₂ disclosed in JP-A-55-136131 is particularly useful in that it gives a high discharge potential of 3.5 V or more to Li and has a high capacity. However, when charge and discharge are repeated, the crystal structure gradually breaks down, and particularly when the depth of charge for occluding Li is deepened, this effect becomes remarkable and the performance deteriorates. Therefore, in terms of charge / discharge cycle characteristics, improvement in potential and capacity stabilization is required as in the case of other positive electrode materials. Therefore, in order to improve charge / discharge characteristics and cycleability, a method using a composite oxide in which a polyvalent transition metal or the like is further added to the above composition is disclosed in JP-A-4-61760 and JP-A-4-1-1.
62357, JP-A-3-2013568, and JP-A-4-4-2.
67053 and the like. However, these methods have the effect of improving the cycleability such as stabilization of the potential, but on the other hand, it often becomes a problem that the initial performance of the battery such as the capacity and the discharge potential is deteriorated.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a lithium ion non-aqueous electrolyte secondary battery excellent in charge / discharge characteristics and cycle performance of a positive electrode active material. .

[0004]

The object of the present invention is to provide a positive electrode,
In a non-aqueous battery comprising a negative electrode and a non-aqueous electrolyte, the positive electrode has a chemical formula of Lix My Gez Op (M is Co, Mn,
One or more transition metal elements selected from Ni, 0.9 ≦ x
≦ 1.3, 0.2 ≦ y ≦ 2.0, 0.01 ≦ z ≦ 0.
2, 2.0 ≦ p ≦ 4.5), which is achieved by a lithium ion type non-aqueous electrolyte secondary battery using an active material of a composite oxide.

The positive electrode active material used in the present invention is LiMO ₂
Alternatively, LiM ₂ O ₄ (M is a transition metal selected from Co, Mn, and Ni) is used as a basic composition, and a Ge compound is added to this as a trace amount dopant. Ge has an atomic radius (1.23Å) almost similar to that of transition metals such as Co, Ni, and Mn, and is considered to easily replace the metal in the structure of LiMO ₂ to form a partial network structure by GeO _2. . It is considered that this network structure contributes to stabilization of capacity and improvement of cycleability by creating a soft field that is advantageous for diffusion of Li.

G effective as a dopant for improving battery performance
The addition concentration of e is limited to the following range. That is, L
structure represented by ix My Gez Op (M is Co, Mn,
One or more transition metal elements selected from Ni),
0.9 ≦ x ≦ 1.3, 0.8 ≦ y ≦ 2.0, 0.01 ≦
The ranges are z ≦ 0.2 and 2.0 ≦ p ≦ 4.5. The addition fraction of z exceeding 0.2 is not effective for the battery performance because the capacity is reduced. Among these ranges, the range of addition of Ge which is desirable for further improving the cycle property is 0.01 ≦
z ≦ 0.1. Ge is LiCoO ₂ , LiNi
Although the addition of O ₂ and LiMn ₂ O ₄ to the positive electrode having a basic structure contributes to the improvement of the cycle property, the performance improvement is particularly remarkable in the addition to LiCoO ₂ , and therefore, the composition of the preferred active material of the present invention. Is LixCoy Gez O
Is.

The positive electrode active material of the present invention is mainly composed of secondary particles having an average particle diameter of 0.1 micron or more and 15 micron or less, which is an aggregate of primary particles having an average particle diameter of 0.01 micron or more and 5.0 micron or less. More preferably, it is preferably composed of primary particle aggregates having an average particle diameter of 1 micron or more and 9.5 micron or less, which is an aggregate of primary particles having an average particle diameter of 0.1 micron or more and 2.5 micron or less,
Particularly preferably, it is preferable to be composed of primary particle aggregates having an average particle diameter of 3.5 to 9.5 microns, which is an aggregate of primary particles having an average particle diameter of 0.1 to 2.5 microns. Further, in the above-mentioned primary particle aggregate, 80% or more of the total volume preferably has a particle size of 1 micron or more and 15 microns or less, and more preferably 8% of the total volume.
It is 5% or more, more preferably 90% or more of the total volume. The average particle size referred to here is a mode diameter indicating the most frequent point, and is an average value of values visually observed from an electron micrograph in a primary particle, and a particle size distribution measuring device in a primary particle aggregate. It is the value measured by.

The specific surface area of the active material in the positive electrode is 0.1.
m ² / is preferably g or less larger than 25 m ² / g, more preferably greater than 1.0m ² / g 25m ² /
g or less, particularly preferably more than 3.0 m ² / g and 25 m ² / g or less.

The negative electrode of the present invention stores lithium ions,
A releasable active material is used. These are alkali metals or their alloys, carbonaceous materials, or Li
p MOr (where M is at least one of Ti,
Transition metals including V, Mn, Co, Fe, Nb, Mo, p
= 0 to 3.1, r = 1.6 to 4.1) is preferable, and the lithium-containing transition metal oxide represented by the formula (1) is preferable. As the alkali metal or its alloy, Li metal, Li-Al alloy, Li -Mg alloy, Li-Al-Ni alloy, Li-A
It is an l-Mn alloy, and it is effective to use a Li metal or a Li-Al alloy among them. As the carbonaceous material, graphite, natural graphite, artificial graphite or the like can be used.

A preferred lithium-containing transition metal oxide used as the negative electrode is Lip M ₁ q1 M ₂ q2 Mnqn Or
(Here, M is at least one of Ti, V, Mn, Co,
The transition metal containing Ni and Fe p = 0 to 3.1, q1 +
q2 + ... + qn = 1, n = 1 to 10, r = 1.6 to
4.1). The most preferable lithium-containing transition metal oxide used for the negative electrode is Lip Coq.
V ₁ -q Or, Lip Niq V ₁ -q Or (where p = 0.
3 to 2.2, q = 0.02 to 0.7, r = 1.5 to 2.
5) can be given. The most preferable lithium-containing transition metal oxides are Lip CoVO ₄ and Lip Ni.
VO ₄ (here, p = 0.3 to 2.2) can be mentioned. The second preferred negative electrode material next to the above-mentioned lithium-containing transition metal oxide is a carbonaceous material which is advantageous in that it causes less precipitation of lithium.

In the present invention, it is preferable that the positive electrode active material and the negative electrode active material have different composition formulas. The positive electrode active material and the negative electrode active material used in the present invention can be achieved by combining compounds having different standard redox potentials. Therefore, it is essentially different from the secondary battery as described in JP-A-1-120,765, in which an active material in which "a positive electrode and a negative electrode are indistinguishable" is combined. The shape of the positive electrode active material of the present invention can be obtained by a method of synthesizing by mixing and firing a lithium compound and a transition metal compound, or a method of washing with water, methanol or the like after firing.

The positive electrode active material used in the present invention is Li, C
Powders of oxides or carbonates of o, Mn, Ni, and Ge are used as raw materials, which are selected and uniformly mixed, and then synthesized by a usual method of melting and firing in the atmosphere. Typical raw materials are Li ₂ CO ₃ , CoCO ₃ , MnO ₂ and NiC.
O ₃ and GeO ₂ . The firing temperature is 400 ° C to 1
It is in the range of 500 ° C, preferably 700 ° C to 1000
It is in the range of ° C. More preferably 750 ° C to 900 ° C
Is the range.

The positive electrode active material and the negative electrode active material of the present invention can be synthesized by a solution reaction in addition to the method of mixing and firing a lithium compound and a transition metal compound.
The firing method is preferred. The firing temperature is in the range of 400 ° C to 1500 ° C, preferably 700 ° C to 1000 ° C, and the firing time is preferably 4 to 48 hours,
It is more preferably 6 to 20 hours, particularly preferably 6 hours.
~ 15 hours. The firing gas atmosphere used in the present invention is not particularly limited, but the positive electrode active material is in air or in a gas containing a large proportion of oxygen (for example, about 30% or more),
The negative electrode active material is preferably in the air or a gas having a low oxygen content (for example, about 10% or less) or an inert gas (nitrogen gas, argon gas). The shape of the positive electrode active material of the present invention can be obtained by a method of synthesizing by mixing and firing a lithium compound and a transition metal compound, or a method of washing with water, methanol or the like after firing.

The positive electrode active material and the negative electrode active material of the present invention are preferably synthesized by firing a mixture of a lithium compound and a transition metal compound described below. Examples of the lithium compound include oxygen compounds, oxyacid salts and halides. As the transition metal compound,
A monovalent to hexavalent transition metal oxide, the same transition metal salt, or the same transition metal complex salt is used.

Preferred lithium compounds used in the synthesis of the active material include lithium hydroxide, lithium oxide, lithium carbonate, lithium nitrate, lithium sulfate, lithium sulfite, lithium phosphate, lithium tetraborate, lithium chlorate and lithium perchlorate. , Lithium thiocyanate, lithium formate, lithium acetate, lithium oxalate, lithium citrate, lithium lactate, lithium tartrate, lithium pyruvate, lithium trifluoromethanesulfonate, lithium tetraborate, lithium hexafluorophosphate, lithium fluoride, Examples thereof include lithium chloride, lithium bromide and lithium iodide.

A preferred transition metal compound is T
iO ₂ (rutile or anatase type), lithium titanate, acetylacetonato titanyl, titanium tetrachloride, titanium tetraiodide, titanyl ammonium oxalate, VOd (d = 2)
~ 2.5 d = 2.5 compound is vanadium pentoxide),
VOd lithium compound, vanadium hydroxide, ammonium metavanadate, ammonium orthovanadate,
Ammonium pyrovanadate, vanadium oxosulfate,
Vanadium oxytrichloride, vanadium tetrachloride, lithium chromate, ammonium chromate, cobalt chromate,
Chromium acetylacetonate, MnO ₂ , Mn ₂ O ₃ ,
Manganese hydroxide, manganese carbonate, manganese nitrate, manganese sulfate, ammonium manganese sulfate, manganese sulfite,
Manganese phosphate, manganese borate, manganese chlorate, manganese perchlorate, manganese thiocyanate, manganese formate,
Manganese acetate, manganese oxalate, manganese citrate, manganese lactate, manganese tartrate, manganese stearate, manganese fluoride, manganese chloride manganese bromide, manganese iodide, manganese acetylacetonate, iron oxide (2, 3
Valence), iron trioxide, iron hydroxide (2,3 valence), iron chloride (2,3 valence), iron bromide (2,3 valence), iron iodide (2,3 valence)
Value), iron sulfate (2,3 value), ammonium iron sulfate (2,3)
Trivalent), iron nitrate (2,3 valent) iron phosphate (2,3 valent), iron perchlorate, iron chlorate, iron acetate (2,3 valent), iron citrate (2,3 valent), citric acid Ammonium iron oxide (2,3 valent, iron oxalate (2,3 valent), ammonium iron oxalate (2,3 valent),
CoO, Co ₂ O ₃ Co ₃ O ₄ , LiCoO ₂ , cobalt carbonate, basic cobalt carbonate, cobalt hydroxide, cobalt sulfate, cobalt nitrate, cobalt sulfite, cobalt perchlorate, cobalt thiocyanate, cobalt oxalate, cobalt acetate, Cobalt fluoride, cobalt chloride, cobalt bromide, cobalt iodide, hexaamminecobalt complex salt (as salts,
Sulfuric acid, nitric acid, perchloric acid, thiocyanic acid, oxalic acid, acetic acid, fluorine, chlorine, bromine, iodine, nickel oxide, nickel hydroxide, nickel carbonate, basic nickel carbonate, nickel sulfate nickel nitrate nitrate, nickel fluoride, nickel chloride , Nickel bromide, nickel iodide, nickel formate, nickel acetate, nickel acetylacetonate, copper oxide (1, 2 valent, copper hydroxide, copper sulfate, copper nitrate, copper phosphate, copper fluoride, copper chloride, ammonium chloride) Copper, copper bromide, copper iodide, copper formate, copper acetate, copper oxalate, copper citrate, niobium oxychloride, niobium pentachloride,
Niobium pentaiodide, niobium monoxide, niobium dioxide, niobium trioxide, niobium pentoxide, niobium oxalate, niobium methoxide,
Niobium ethoxide, niobium propoxide, niobium butoxide, lithium niobate, MoO ₃ , MoO ₂ , LiM
o ₂ O ₄ , molybdenum pentachloride, ammonium molybdate, lithium molybdate, ammonium molybdophosphate, molybdenum acetylacetonate oxide, WO ₂ , W
O ₃ , tungstic acid, ammonium tungstate,
Tungsto ammonium phosphate can be used.

Particularly preferred transition metal compounds used for synthesizing the positive electrode active material in the present invention are MnO ₂ and Mn ₂
O ₃ , manganese hydroxide, manganese carbonate, manganese nitrate,
Ammonium manganese sulfate, manganese acetate, manganese oxalate, manganese citrate, CoO, Co ₂ O ₃ , Co ₃ O
₄ , LiCoO ₂ , cobalt carbonate, basic cobalt carbonate, cobalt hydroxide, cobalt oxalate, cobalt acetate, nickel oxide, nickel hydroxide, nickel carbonate, basic nickel carbonate, nickel sulfate, nickel nitrate, nickel acetate. .

Among these, particularly preferred combinations of lithium compounds and transition metal compounds are lithium hydroxide, lithium carbonate, lithium acetate, MnO ₂ , Mn ₂ O ₃ ,
Manganese hydroxide, manganese carbonate, manganese nitrate, Co
O, Co ₂ O ₃ , Co ₃ O ₄ , LiCoO ₂ , cobalt carbonate, basic cobalt carbonate, cobalt hydroxide, cobalt sulfate, cobalt nitrate, nickel oxide, nickel hydroxide,
Examples thereof include nickel carbonate, basic nickel carbonate, nickel sulfate, nickel nitrate, and nickel acetate.

Examples of a preferable Ge raw material used for synthesizing the positive electrode active material of the present invention include metal Ge and Ge.
O ₂ , Ge (OH) ₂ , GeS ₂ , Ge (OH) ₄ , Ge
(NH) ₂ , Li ₄ GeO ₄ is used. Particularly preferred is GeO ₂ . These are used for synthesis by adding and mixing the above lithium compound and transition metal compound and firing.

The negative electrode active material used in the present invention can be obtained by chemically inserting lithium ions into a negative electrode active material precursor of a transition metal oxide and / or a lithium-containing transition metal oxide. For example, a method of reacting with lithium metal, a lithium alloy, butyl lithium, or the like, or electrochemically inserting lithium ions is preferable. In the present invention, it is particularly preferable to electrochemically insert lithium ions into the transition metal oxide that is the negative electrode active material precursor. Above all, it is most preferable to electrochemically insert lithium ions into the lithium-containing transition metal oxide that is the precursor of the negative electrode active material. As a method for electrochemically inserting lithium ions, a lithium-containing transition metal oxide (referred to as a negative electrode active material precursor in the present invention) as a positive electrode active material,
The negative electrode active material can be obtained by discharging a redox system (for example, an open system (electrolysis) or a closed system (battery)) made of a non-aqueous electrolyte containing lithium metal and a lithium salt. Further, as another embodiment example, a lithium-containing transition metal oxide as a positive electrode active material, a negative electrode active material precursor having a composition formula different from that of the positive electrode active material as a negative electrode active material, and an oxidation composed of a non-aqueous electrolyte containing a lithium salt. Most preferred is the method obtained by charging a reducing system (eg open system (electrolysis) or closed system (batteries)).

The amount of lithium ions inserted is not particularly limited, but is 27 to 1340 mA per 1 g of the negative electrode active material precursor.
h (corresponding to 1 to 50 mmol) is preferable. Especially 40 to 1
070 mAh (corresponding to 1.5 to 40 mmol) is preferable.
Further, 54 to 938 mAh (corresponding to 2 to 35 mmol) is most preferable. The cut-off voltage of the charge / discharge cycle cannot be uniquely determined because it changes depending on the type and combination of the positive electrode active material and the negative electrode active material used, but the discharge voltage can be increased and the cycleability can be substantially maintained. For, a charging voltage of 4.5 to 4.0 V with respect to Li is preferable.

The structure of the compound obtained by firing by the method of the present invention was analyzed based on the X-ray crystal diffraction spectrum, and its chemical formula was as follows: Inductively coupled plasma (ICP) emission spectroscopy It was calculated based on the weight difference of the powder before and after firing.

Preferred specific examples of the positive electrode active material used in the present invention are shown below. 1. Li _1.05 Co _1.0 Ge _0.03 O _2.09 2. Li _1.1 Co _1.0 Ge _0.03 O _2.11 3. Li _0.95 Co _1.0 Ge _0.03 O _2.04 4. Li _1.05 Co _0.95 Ge _0.03 O _2.00 5. Li _1.05 Co _0.95 Ge _0.05 O _2.05 6. Li _1.05 Co _1.0 Ge _0.08 O _2.19 7. Li _1.05 Co _1.0 Ge _0.15 O _2.33 8. Li _1.05 Ni _1.0 Ge _0.03 O _2.09 9. Li _1.05 Ni _1.0 Ge _0.06 O _2.15 10. Li _1.00 Mn _2.0 Ge _0.03 O _4.06 11. Li _1.00 Mn _2.0 Ge _0.06 O _4.12

As the negative electrode active material which can be used in combination with the present invention, lithium metal and lithium alloy (Al, A
1-Mn (US Pat. No. 4,820,599), Al-M
g (JP-A-57-98977), Al-Sn (JP-A-Sho 6)
3-6, 742), Al-In, Al-Cd (Japanese Unexamined Patent Publication No.
-144,573) or the like, or a calcined carbonaceous compound capable of inserting and extracting lithium ions or lithium metal (for example,
JP-A-58-209,864, 61-214,41
7, the same 62-88, 269, the same 62-216, 170,
63-13, 282, 63-24, 555, 63
-121,247, 63-121,257, 63-
155, 568, 63-276, 873, 63-3
14,821, JP-A-1-204,361, and 1-22.
1, 859, 1-259, 360, etc.). The purpose of the combined use of the lithium metal and lithium alloy is to insert lithium ions in the battery,
The battery reaction does not utilize the dissolution / precipitation reaction of lithium metal or the like.

A conductive agent, a binder, a filler and the like can be added to the electrode mixture. The conductive agent may be any electron-conductive material that does not cause a chemical change in the constructed battery. Usually, natural graphite (scaly graphite, flake graphite, earthy graphite, etc.), artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers and metals (copper, nickel, aluminum, silver (JP-A-63) -1
48, 554), powders, metal fibers, or polyphenylene derivatives (Japanese Patent Laid-Open No. 59-20971) can be included as one kind or a mixture thereof. The combined use of graphite and acetylene black is particularly preferred. The amount added is not particularly limited, but is preferably 1 to 50% by weight, and particularly preferably 2 to 30% by weight. For carbon and graphite, 2 to 15% by weight is particularly preferable.

The binder is usually starch, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, diacetyl cellulose, polyvinyl chloride, polyvinylpyrrolidone,
Tetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber, polybutadiene, fluororubber,
Polysaccharides such as polyethylene oxide, thermoplastic resins, polymers having rubber elasticity and the like are used alone or as a mixture thereof. When a compound containing a functional group that reacts with lithium, such as a polysaccharide, is used, it is preferable to add a compound such as an isocyanate group to deactivate the functional group. The amount of the binder added is not particularly limited, but is preferably 1 to 50% by weight, and particularly preferably 2 to 30% by weight. As the filler, any fibrous material that does not cause a chemical change in the constructed battery can be used. Generally, olefin polymers such as polypropylene and polyethylene, fibers such as glass and carbon are used. The amount of the filler added is not particularly limited, but is preferably 0 to 30% by weight.

As the electrolyte, propylene is used as an organic solvent.
Len carbonate, ethylene carbonate, butylene car
Carbonate, dimethyl carbonate, diethyl carbonate
, Γ-butyrolactone, 1,2-dimethoxyethane
Amine, tetrahydrofuran, 2-methyltetrahydrofuran
Amine, dimethyl sulfoxide, 1,3-dioxolane,
Formamide, dimethylformamide, dioxolane,
Acetonitrile, nitromethane, methyl formate, methyl acetate
And phosphoric acid triester (JP-A-60-23,97)
3), trimethoxymethane (JP-A-61-4,17)
0), a dioxolane derivative (JP-A-62-15,77).
1, 62-222, 372, 62-108, 474),
Sulfolane (JP-A-62-31959), 3-methyl
-2-Oxazolidinone (JP-A-62-44,96)
1), a propylene carbonate derivative (JP-A-62-2)
90,069, 62-290,071), tetrahydr
Rofuran derivative (JP-A-63-32,872), diet
Luether (JP-A-63-62,166), 1,3-type
Such as LOPAN SALTON (JP-A-63-102,173)
Mixed with at least one aprotic organic solvent
Solvents and lithium salts that are soluble in the solvent, such as LiCl
O_Four, LiBF₆, LiPF₆, LiCF₃SO₃, L
iCF ₃CO₂, LiAsF₆, LiSbF₆, LiB
_TenCl_Ten(JP-A-57-74,974), lower aliphatic carbs
Lithium rubonate (JP-A-60-41,773), Li
AlCl_Four, LiCl, LiBr, LiI (JP-A-60
247,265), lithium chloroborane (Japanese Patent Application Laid-Open No. 6-242242).
1-165,957), lithium tetraphenylborate (special
Consists of one or more salts such as Kai 61-214, 376)
Is made. Among them, there is propylene carbonate
And ethylene capote and 1,2-dimethoxyethane and
And / or LiCF in a mixture of diethyl carbonate
₃SO₃, LiClO_Four, LiBF_FourAnd / or
LiPF₆An electrolyte containing is preferred. Charge these electrolytes
The amount added to the pond is not particularly limited, but the positive electrode active material
Use the required amount depending on the amount of negative electrode active material and battery size
be able to. The volume ratio of the solvent is not particularly limited
But propylene carbonate or ethylene carbonate
1,2-dimethoxyethane and / or diethyl
0.4 / 0.6-0.6 for carbonate mixture
/0.4 (1,2-dimethoxyethane and diethyl carbo
The mixing ratio when using both nates is 0.4 / 0.6-
0.6 / 0.4) is preferable. The concentration of supporting electrolyte is
But not limited to 0.2 to 3 per liter of electrolyte
Molar is preferred.

In addition to the electrolytic solution, the following solid electrolyte is also used.
Can be used. As the solid electrolyte, an inorganic solid electrolyte is used.
It is divided into degrading and organic solid electrolyte. For inorganic solid electrolyte
Is often Li nitride, halide, oxyacid salt, etc.
Are known. Above all, Li₃N, LiI, Li_FiveN
I₂, Li₃N-LiI-LiOH, LiSiO_Four, L
iSiO_Four-LiI-LiOH (JP-A-49-81,8
99), xLi₃PO _Four-(1-x) Li_FourSiO
_Four(JP-A-59-60,866), Li₂SiS₃(Special
KAISHO 60-501,731), phosphorus sulfide compounds
62-82, 665) and the like are effective. Organic solid electrolysis
In terms of quality, polyethylene oxide derivatives or those containing
Polymer (Japanese Patent Laid-Open No. 63-135,447), Polypro
A pyrene oxide derivative or a polymer containing the derivative,
Polymers containing an on-dissociative group (JP-A-62-254,30)
2, ibid. 62-254, 303, ibid. 63-193, 95
4), a polymer containing an ionic dissociative group and the above aprotic
Mixtures of electrolytes (US Pat. No. 4,792,504;
4,830,939, JP-A-62-22,375 and 6
2-22, 376, 63-2, 375, 63-2
2,776, JP-A-1-95,117), phosphate ester
Rupolymer (Japanese Patent Laid-Open No. 61-256,573) is effective.
It In addition, add polyacrylonitrile to the electrolyte
There is also a method (JP-A-62-278,774). Also, nothing
Of using a machine with an organic solid electrolyte (JP-A-60-1,
768) is also known.

As the separator, an insulating thin film having a large ion permeability and a predetermined mechanical strength is used. A sheet or non-woven fabric made of olefin polymer such as polypropylene or glass fiber or polyethylene is used because of its resistance to organic solvent and hydrophobicity. The pore size of the separator is in the range generally used for batteries. For example, 0.01 to 10 μ
m is used. The thickness of the separator is generally within the range for batteries. For example, 5 to 300 μm is used.

It is also known to add the following compounds to the electrolyte for the purpose of improving discharge and charge / discharge characteristics. For example, pyridine (JP-A-49-108,52)
5), triethylphosphite (JP-A-47-4,3)
76), triethanolamine (JP-A-52-72,4).
25), cyclic ether (JP-A-57-152,68)
4), ethylenediamine (JP-A-58-87,77)
7), n-glyme (JP-A-58-87,778), hexaphosphoric acid triamide (JP-A-58-87,779),
Nitrobenzene derivative (JP-A-58-214, 28)
1), sulfur (JP-A-59-8,280), quinoneimine dye (JP-A-59-68,184), N-substituted oxazolidinone and N, N'-substituted imidazolidinone (JP-A-5-280).
9-154,778), ethylene glycol dialkyl ether (JP-A-59-205,167), quaternary ammonium salt (JP-A-60-30,065), polyethylene glycol (JP-A-60-41). , 773), pyrrole (JP-A-60-79,677), 2-methoxyethanol-
(JP-A-60-89,075), AlCl3 (JP-A-61-88,466), conductive polymer-monomer of electrode active material (JP-A-61-161,673), triethylenephosphoramide. (JP 61-208,758), trialkylphosphine (JP 62-80,976), morpholine (JP 62-80,977), aryl compound having a carbonyl group (JP 62-86, 67
3), hexamethylphosphoric triamide and 4-alkylmorpholine (JP 62-217,575), bicyclic tertiary amine (JP 62-217,578), oil (JP 62 -287,580), a quaternary phosphonium salt (JP-A-63-121268), a tertiary sulfonium salt (JP-A-63-121269), and the like.

Further, in order to make the electrolytic solution nonflammable, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride chloride can be contained in the electrolytic solution. (JP-A-48-36,
632) Further, carbon dioxide gas can be included in the electrolytic solution in order to have suitability for high temperature storage. (JP-A-59-
134,567)

The mixture of the positive electrode and the negative electrode may contain an electrolytic solution or an electrolyte. For example, the ion conductive polymer or nitromethane (Japanese Patent Laid-Open No. 48-36,6).
33), a method of adding an electrolytic solution (JP-A-57-124,870) is known.

Further, the surface of the positive electrode active material can be modified. For example, the surface of the metal oxide may be treated with an esterifying agent (JP-A-55-163,779),
Treatment with a photocatalyst (JP-A-55-163,780), conductive polymers (JP-A-58-163,188, 59-14).
274), polyethylene oxide, etc. (JP-A-60-
97, 561). Also, the surface of the negative electrode active material can be modified. For example, an ion conductive polymer or polyacetylene layer is provided (JP-A-58-111276), or LiCl
(JP-A-58-142,771) and the like.

The collector of the electrode active material may be any electron conductor as long as it does not undergo a chemical change in the constructed battery. For example, for the positive electrode, in addition to stainless steel, nickel, aluminum, titanium, calcined carbon, etc. as the material, carbon on the surface of aluminum or stainless steel,
Those treated with nickel, titanium or silver, and the negative electrode are made of stainless steel, nickel, copper, titanium,
In addition to aluminum and calcined carbon, copper, stainless steel whose surface is treated with carbon, nickel, titanium, or silver), an Al-Cd alloy, or the like is used. It is also used to oxidize the surface of these materials. The shape is
In addition to the foil, a film, a sheet, a net, a punched product, a lath body, a porous body, a foamed body, a molded body of a fiber group and the like are used. The thickness is not particularly limited, but is 1 to 5
Those having a diameter of 00 μm are used.

The shape of the battery can be any of coins, buttons, sheets, cylinders, corners and the like. In coins and buttons, the mixture of the positive electrode active material and the negative electrode active material is used after being pressed into a pellet shape. The thickness and diameter of the pellet are determined by the size of the battery. In the sheets, cylinders, and corners, the mixture of the positive electrode active material and the negative electrode active material is
It is used after being coated, dried, dehydrated and pressed on the current collector. The coat thickness, length and width are determined by the size of the battery, but the coat thickness in the compressed state after drying is particularly preferably 1 to 2000 μm. As a method for drying or dehydrating the pellets or sheets, a commonly used method may be used, but in particular vacuum, infrared rays, far infrared rays,
Electron beams, low-humidity air, etc. can be used alone or in combination. The temperature is preferably 80 to 350 ° C.
Particularly, 100 to 250 ° C. is preferable. The pellet or sheet pressing method may be a generally used method, but in particular,
A die pressing method and a calendar pressing method are preferable. The pressing pressure is not particularly limited, but is preferably 0.2 to 3 t / cm ² . The press speed of the calendar press method is 1 to 50 m /
min is preferred. The pressing temperature is preferably room temperature to 200 ° C. The mixture sheet is rolled or folded and inserted into a can, the can and the sheet are electrically connected, an electrolytic solution is injected, and a sealing plate is used to form a battery can. At this time, the safety valve can be used as a sealing plate. For the can and the lead plate, a metal or alloy having electrical conductivity can be used. For example, metals such as iron, nickel, titanium, chromium, molybdenum, copper and aluminum or alloys thereof are used. As the sealing agent for sealing, a conventionally known compound or mixture such as asphalt can be used.

[0036]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the examples as long as the gist of the invention is not exceeded.

Example 1 (Production of electrode mixture, coin battery and charge / discharge test) The positive electrode material was 102% by weight of the positive electrode active material, 12% by weight of flake graphite as a conductive agent, and tetrafluorocarbon as a binder. A positive electrode mixture prepared by mixing ethylene at a mixing ratio of 6% by weight was compression-molded to form a positive electrode pellet (13 mmΦ, 0.0
6 g) was prepared, and this was put in a dry box (dew point -40 to 40).
It was used after being thoroughly dehydrated and dried for 2 hours or more on a far-infrared heater in (-70 ° C dry air). The negative electrode material is a lithium / aluminum alloy (thickness 0.7 mm, 15 mmΦ,
0.066 g) was used. 80 μm thick SU for the current collector
Using the net of S316, this was welded to positive and negative electrode cans for coin batteries, respectively. As an electrolyte, 250 μl of an equal volume mixture of ethylene carbonate containing 1 mol / liter LiPF ₆ and diethylene carbonate was used, and this was impregnated into a separator made of a microporous polypropylene sheet and a polypropylene nonwoven fabric. Coin type lithium ion battery with positive and negative electrode materials set on the current collector, a separator inserted between the positive and negative electrodes, and the positive and negative electrode cans joined together using a caulking machine in a dry box. Was produced. Using this lithium-ion battery, 1.0 mA /
A charge / discharge test was performed at a constant current density of cm ² . All tests started with charging. The charge / discharge cycle property was evaluated by setting a charge cutoff voltage of 4.5 V and a discharge cutoff voltage of 3.0 V, and cycling between 4.5 V and 3.0 V.

(Preparation of Active Material) Comparative Sample 1 Lithium carbonate and cobalt carbonate were mixed so that the atomic ratio of lithium and cobalt was 1.2: 1.0, and the mixture was heated to 800 ° C. in air.
After baking at 10 ° C for 10 hours, cooling at 3 ° C / min, Li _1.2 C
I got oO _2.1 . The comparative sample was assembled into a coin-type battery as a positive electrode pellet by the above method, and a charge / discharge test was carried out. As samples of the present invention and comparative samples having different Ge contents, lithium carbonate, sodium carbonate, and germanium dioxide (GeO ₂ ) were mixed in an automatic mortar so that the atomic ratio of the three elements lithium: cobalt: germanium would be the following composition ratio. After mixing and firing in air at 800 ° C. for 10 hours, the mixture was cooled at 3 ° C./min to synthesize a Ge-containing composite oxide for a positive electrode.

Composition of Positive Electrode Active Material Comparison 1 Li _1.2 Co _1.0 O _2.1 Invention 1 Li _1.05 Co _1.0 Ge _0.03 O _2.09 Invention 2 Li _1.1 Co _1.0 Ge _0.03 O _2.11 Invention 3 Li _0.95 Co _1.0 Ge _0.03 O _2.04 Invention 4 Li _1.05 Co _0.95 Ge _0.03 O _2.00 Invention 5 Li _1.05 Co _0.95 Ge _0.05 O _2.05 Invention 6 Li _1.05 Co _1.0 Ge _0.08 O _2.19 Invention 7 Li _1.05 Co _1.0 Ge _0.15 O _2.33 Comparison 2 Li _1.05 Co _1.0 Ge _0.25 O _2.53 Comparison 3 Li _1.05 Co _1.0 Ge _0.30 O _2.63 Table 1 summarizes the results of evaluation of charge / discharge characteristics and cycle performance of the above samples. Here, the composition of the synthetic active material is I
Calculated based on CP. As is clear from this result,
It can be seen that in the sample in which Ge is added to the active material having the composition of LiCoO _2, the discharge potential is improved and the cycle property (capacity retention rate) of the discharge potential is improved, so that the charge / discharge performance is improved. The preferable addition amount of Ge for performance improvement is 3 to
It is in the region of 5 mol%, and as shown in Comparative Examples 2 and 3, in the range where the Ge addition amount exceeds 20%, the battery capacity decreases, and the object of the present invention cannot be satisfied.

Example 2 (Combination of Composite Transition Metal Oxide with Negative Electrode) Instead of the negative electrode material (Li / Al) used in Example-1,
82% by weight of LiCoVO ₄ as a lithium-containing transition metal compound, 12% by weight of scaly graphite as a conductive agent, and 6% by weight of polyvinylidene fluoride as a binder were mixed in a mixture ratio, and a negative electrode pellet was compression-molded. (13 mm
Φ, 0.060g) in the dry box middle far-red line heater
A coin cell was produced in the same manner as in Example 1 except that the one sufficiently dried in 1. was used as a common negative electrode, and the charge / discharge performance and cycleability thereof were evaluated.

As a result, although the cycleability of the discharge capacity as a whole is inferior to the case where Li / Al is used for the negative electrode, Ge
Regarding the effect of addition of the above, the same tendency of cycle property improvement (stabilization of potential and capacity) as the result of Table 1 was obtained for the comparative sample, and the superiority of the positive electrode active material by the composition of the present invention was confirmed.

Example 3 Manganese dioxide or nickel carbonate was used as a synthetic raw material in place of the cobalt carbonate used in the synthesis in Example 1, and the following composition was obtained under firing conditions of 500 ° C. to 900 ° C. for 6 to 10 hours. Various composite oxides according to Positive Electrode Active Material Composition Comparison 4 Li _1.05 Ni _1.0 O _2.02 Comparison 5 Li _1.05 Mn _2.0 O _4.02 Invention 8 Li _1.05 Ni _1.0 Ge _0.03 O _2.09 Invention 9 Li _1.05 Ni _1.0 Ge _0.06 O _2.15 Invention 10 Li _1.00 Mn _2.0 Ge _0.03 O _4.06 Invention 11 Li _1.00 Mn _2.0 Ge _0.06 O _4.12

The pellets of the above active material were used as the positive electrode, and the charge / discharge characteristics of the coin battery prepared by using Li / Al for the negative electrode in the same manner as in Example 1 were evaluated. As a result, the comparative samples 4 and 5 gave a low initial discharge capacity to the comparative sample 1 having Co as a transition metal, but the comparative samples 4 and 5 of the present invention samples 8 to 11 using Ge.
On the other hand, in all cases, the improvement of the cycle property was confirmed especially in the stabilization of the discharge capacity.

Table 1 Discharge capacity Average discharge voltage After 50 cycles After 50 cycles mAh V vs. Li / Al capacity retention rate (%) Potential retention rate (%) Comparison 1 9.0 3.90 67.7 96. 0 Present invention 1 9.0 4.02 75.0 99.2 Present invention 2 8.9 4.01 72.0 99.0 Present invention 3 9.0 4.02 75.0 99.0 Present invention 48 4.8 4.02 74.0 99.2 Invention 5 8.2 4.00 75.0 97.0 Invention 6 8.0 3.95 72.0 97.0 Comparison 2 6.8 3.90 70 .0 96.5 Comparison 3 6.5 3.90 71.0 96.5

[0045]

By using the positive electrode active material of the present invention, a non-aqueous battery having improved charge / discharge cycle characteristics can be obtained.

[Procedure amendment]

[Submission date] October 22, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

The specific surface area of the active material in the positive electrode is 0.1.
Preferably m ² / g or less larger than 25 m ² / g, more preferably greater than 0.1m ² / g 5m ² / g
Or less, particularly preferably greater than 0.1 m ² / g and 3
m ² / g or less.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0045

[Correction method] Change

[Correction content]

[0045]

By using the positive electrode active material of the present invention, a non-aqueous electrolyte secondary battery having improved charge / discharge cycle characteristics can be obtained.

Claims (6)

[Claims] 1. A non-aqueous battery comprising a positive electrode, a negative electrode and a non-aqueous electrolyte, wherein the positive electrode has the chemical formula Lix My Ge O.
p (M is one or more transition metal elements selected from Co, Mn, and Ni, 0.9 ≦ x ≦ 1.3, 0.8 ≦ y ≦ 2.0,
0.01 ≦ z ≦ 0.2, 2.0 ≦ p ≦ 4.5) as the active material, a lithium ion type non-aqueous electrolyte secondary battery. 2. In the chemical formula of the composite oxide, M is Co, and 0.9 ≦ x ≦ 1.3, 0.8 ≦ y ≦ 1.0, 0.0
The non-aqueous electrolyte secondary battery according to claim 1, wherein 1 ≦ z ≦ 0.2 and 2.0 ≦ p ≦ 2.2. 3. The non-aqueous electrolyte secondary battery according to claim 1, wherein the composite oxide active material of the positive electrode has an average particle size of 2.5 μm or less. 4. The non-aqueous electrolyte secondary battery according to claim 1, wherein a composite oxide containing Li, Co, V is used as an active material for the negative electrode. 5. The non-aqueous electrolyte secondary battery according to claim 1, wherein an active material containing a carbonaceous material as a main component is used as the negative electrode. 6. The non-aqueous electrolyte is propylene carbonate,
The non-aqueous electrolyte secondary battery according to claim 1, comprising a mixture of a solvent selected from ethylene carbonate, diethyl carbonate, and methyl propionate and a supporting salt.