JPH07211352A - Nonaqueous secondary battery - Google Patents

Abstract

PURPOSE:To provide a highly safe nonaqueous secondary battery which has high discharge electric potential and high discharge capacity in a wide temperature range and has an excellent charge and discharge cycle characteristic. CONSTITUTION:Oxide to insert and release lithium and nonaqueous electrolyte obtained by dissolving fluorine-contained lithium salt in mixed solvent containing ethylene carbonate by 5 volume % to 30 volume % and diethyl carbonate in nonaqueous electrolyte, are used as a negative electrode active material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous secondary battery having improved charge / discharge characteristics such as discharge potential, discharge capacity and charge / discharge cycle life and safety.

[0002]

2. Description of the Related Art When lithium metal or a lithium alloy is used as a negative electrode active material as an electrolyte for a non-aqueous secondary battery, ethylene carbonate (EC) and cyclic or acyclic ethers having a lower viscosity than EC are used. (For example, THF,
Dioxolane (DOL), 2-methyltetrahydrofuran, dimethoxyethane (DME)) (JP-A-59-96)
666), organic electrolytes based on organic esters (for example, methyl formate) (JP-A-1-309261), asymmetric acyclic carbonates (for example, methyl ethyl carbonate) (JP-A-4-104468), EC and 2-methyltetrahydrofuran and butylene carbonate (BC)
Non-aqueous secondary batteries using (US Pat. No. 5,079,109) and the like can be mentioned. When a carbonaceous material is used as the negative electrode active material, a mixed solvent of cyclic carbonic acid ester and cyclic ester (for example, propylene carbonate (PC)) is used as the electrolytic solution.
And γ-butyrolactone (BL)) and LiXFn (X:
B, P, As, Sb, n: 4 or 6) (Japanese Patent Laid-Open No. 2-2
15059), a mixed solvent of cyclic carbonic acid ester and chain ester (for example, PC and MA) and LiXFn (X: B,
P, As, Sb, n: 4 or 6) (JP-A-3-295)
178), a mixed solvent of a cyclic ester, an ester, a chain ester, and a cyclic ether to which an amide compound is added (JP-A-4-115471), a solvent containing a chain carbonate and a cyclic carbonate (JP-A-4-115471). 17167
4, JP-A-5-13088), non-aqueous secondary batteries using EC and DMC (US Pat. No. 5,192,629), and the like. When a transition metal oxide is used as the negative electrode active material, it is described in EP567149A. JP-A-3
-291862. When SnO ₂ is used as the positive electrode active material of the primary battery, a non-aqueous battery using PC and LiClO ₄ and the like can be mentioned (electrochemistry and industrial physics, vol. 46, No. 7, page 407, 1978).

[0003]

An object of the present invention is to provide a highly safe non-aqueous secondary battery having a high discharge potential and a high discharge capacity at both room temperature and low temperature and further having good charge / discharge cycle characteristics. Is to provide.

[0004]

The object of the present invention relates to a non-aqueous secondary battery comprising a positive electrode active material, a negative electrode active material and a non-aqueous electrolyte, wherein at least one of the negative electrode active materials has lithium inserted and released. And a non-aqueous electrolyte in which a lithium salt containing fluorine is dissolved in a mixed solvent containing 5% by volume or more and less than 30% by volume of ethylene carbonate and diethyl carbonate. Achieved by a non-aqueous secondary battery.

The mixed solvent used in the electrolyte of the present invention is 5
Ethylene carbonate of not less than 30% by volume and not less than 30% by volume,
It is a mixed solvent containing diethyl carbonate. The mixed solvent may contain only any chain ester carbonate. By using only the chain carbonic acid ester together with ethylene carbonate, the discharge capacity at low temperature and the charge / discharge cycle life can be significantly improved.

Examples of the chain carbonic acid ester other than diethyl carbonate which can be used in the present invention include dimethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate and the like, but preferably the number of carbon atoms is It is a chain carbonic acid ester of 3 to 8. More preferably, dimethyl carbonate, dipropyl carbonate,
Methyl ethyl carbonate, methyl propyl carbonate and ethyl propyl carbonate are more preferable, dimethyl carbonate and methyl ethyl carbonate are more preferable, and dimethyl carbonate is particularly preferable.

Preferred examples of the mixed solvent used in the electrolyte of the present invention include 5% by volume or more and less than 30% by volume of ethylene carbonate and diethyl carbonate, or 5% by volume or more and less than 30% by volume of ethylene carbonate and diethyl carbonate. A mixed solvent containing at least one chain carbonic acid ester selected from dimethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, methyl propyl carbonate and ethyl propyl carbonate can be mentioned.

A more preferable example is 5% by volume or more and 3
Less than 0% by volume of ethylene carbonate and diethyl carbonate, or 5% by volume or more and less than 30% by volume of ethylene carbonate and diethyl carbonate, and at least one chain carbonate ester selected from dimethyl carbonate, dipropyl carbonate and methyl ethyl carbonate. And a mixed solvent containing.

More preferred examples are selected from ethylene carbonate and diethyl carbonate in an amount of 5% by volume to less than 30% by volume, or ethylene carbonate, diethyl carbonate in an amount of 5% by volume to less than 30% by volume, dimethyl carbonate, and methylethyl carbonate. A mixed solvent containing at least one chain carbonic acid ester may be mentioned.

In the present invention, ethylene carbonate is 5% by volume or more and less than 30% by volume of the mixed solvent, more preferably 5% by volume or more and 25% by volume or less, and particularly preferably 10% by volume or more and 25% by volume or less. Most preferably, it is 10% by volume or more and 20% by volume or less. The chain carbonate is more than 70% by volume and 95% by volume or less of the mixed solvent, more preferably 75% by volume or more and 95% by volume or less,
It is particularly preferably 75% by volume or more and 90% by volume or less.
Most preferably, it is 80% by volume or more and 90% by volume or less. In the chain carbonic acid ester, the mixing ratio of diethyl carbonate and other chain carbonic acid ester is not particularly limited, but preferably diethyl carbonate is 10 to 95% by volume, preferably 10 to 80% by volume, particularly Preferably 1
It is 0 to 70% by volume.

The lithium salt used in the electrolyte of the present invention is
It is a lithium salt containing fluorine, and as a specific example, LiB
F_Four, LiPF₆, LiAsF₆, LiSbF₆, Li
CF ₃SO₃, LiCF₃CO₂Etc.
It is not particularly limited to these compounds. Preferably
The lithium salt used is LiCF₃SO₃, LiXFn
(X: B, P, As, Sb, n is 4 when X is B and X is
In case of P, As, Sb, it is 6). LiXFn is a Lewis acid double salt represented by LiF + XFn-1-> LiXFn, and specific examples include LiBF
_Four, LiPF₆, LiAsF₆, LiSbF₆Are listed
Be done. More preferably LiBF_Four, LiPF₆, Li
CF₃SO₃And particularly preferably LiPF₆, L
iCF₃SO₃And most preferably LiPF₆And
It

The lithium salt used in the electrolyte of the present invention is
It can be mixed and used. Preferably LiPF
₆And LiCF₃SO₃, LiXFn (X: B, As,
Sb and n are 4 when X is B and 6 when X is As and Sb)
A mixture with at least one lithium salt selected from
It More preferably LiPF₆And LiBF_Four, Li
CF₃SO₃At least one lithium salt selected from
Mixed with. Particularly preferably LiPF₆And LiBF
_FourMixed with. In the present invention, a lithium salt is mixed and used.
If present, they can be mixed in any ratio. Good
More preferably, the second and subsequent lithium salts occupy the entire lithium salt.
The molar ratio is more than 0% and 45% or less, which is more preferable.
It is more than 0% and 30% or less. More preferably
2% or more and 30% or less, most preferably 5% or more and 25% or less
Below. Preferred Lithium Salt Combinations of the Invention
Is LiPF₆And LiCF₃SO ₃, LiXFn
(X: B, As, Sb, n is 4 when X is B and X is A
For s and Sb, at least one type of lithium selected from 6)
LiPF in combination with um salt ₆Is less than 100% 4
5% or less, and more preferably LiPF₆And L
iBF_Four, LiCF₃SO₃At least 1 selected from
LiPF in combination with some lithium salts₆Is 100
% And 40% or less. Particularly preferably, LiPF ₆
And LiBF_FourIn combination with LiPF₆Is 100%
It is less than 35% or less.

In the present invention, the concentration of the lithium salt in the electrolyte is not particularly limited, but is preferably 0.2 M to 3 M, particularly preferably 0.5 M to 2 M, most preferably 0.
It is 6M-1.5M.

The amount of these electrolytes to be added into the battery is not particularly limited, but it can be used in the required amount depending on the amount of the positive electrode active material or the negative electrode active material and the size of the battery.

In addition to the electrolytic solution, the following solid electrolytes can be used. Solid electrolytes are classified into inorganic solid electrolytes and organic solid electrolytes. Li-nitrides, halides, oxyacid salts, and the like are well known as inorganic solid electrolytes. Among them, Li ₃ N, LiI, Li ₅ N
_{I 2, Li 3 N-LiI} -LiOH, LiSiO 4, L
iSiO ₄ -LiI-LiOH (JP-A-49-8189)
9 _{JP), xLi 3 PO 4 - (} 1-x) Li 4 SiO
₄ (Japanese Patent Laid-Open No. 59-60866), Li ₂ SiS ₃
(JP-A-60-501731), phosphorus sulfide compounds (JP-A-62-82665) and the like are effective.
In the organic solid electrolyte, a polyethylene oxide derivative or a polymer containing the derivative (JP-A-63-135447), a polypropylene oxide derivative or a polymer containing the derivative, a polymer containing an ion dissociating group (JP-A-62-254302). JP-A-62-2543
03, JP-A-63-193954), a mixture of a polymer containing an ionic dissociative group and the aprotic electrolyte (US Pat. No. 4,792,504, US Pat. No. 4,830,939, JP JP-A-62-22375,
JP-A-62-22376, JP-A-63-2237
5, JP-A-63-22776, JP-A-1-
95117), a phosphoric acid ester polymer (Japanese Patent Laid-Open No. 61-256573), and a polymeric matrix material containing an aprotic polar solvent (US Pat.
822,70, U.S. Pat. No. 4,830,939,
JP-A-63-239779, Japanese Patent Application No. 2-3031
No. 8 and Japanese Patent Application No. 2-78531) are effective. Further, there is also a method of adding polyacrylonitrile to the electrolytic solution (Japanese Patent Laid-Open No. 62-278774). In addition, a method of using both an inorganic and an organic solid electrolyte in combination (Japanese Patent Laid-Open No. Sho 60
No. -1768) is also known.

The positive electrode active material used in the present invention is not particularly limited as long as it can reversibly store and release lithium ions. The positive electrode active material used preferably is a transition metal oxide, and particularly preferably a lithium-containing transition metal oxide.

Preferred lithium-containing transition metal oxide positive electrode active materials include lithium-containing Ti, V, Cr, and
Examples thereof include oxides containing Mn, Fe, Co, Ni, Cu, Mo and / or W. It is preferable that the positive electrode active material and the negative electrode active material have different composition formulas. Alkali metals other than lithium (elements IA and IIA of the Periodic Table), semimetals Al, Ga, In, Ge, Sn, P
You may mix b, Sb, Bi, etc. Mixing amount is 0 to 1
0 mol% is preferable.

The more preferable lithium-containing transition metal oxide positive electrode active material used in the present invention is the sum of lithium compound / (transition metal compound), where the transition metal is T
It is preferable that the compounds are mixed so that the molar ratio of i, V, Cr, Mn, Fe, Co, Ni, Mo and W) is 0.3 to 2.2.

As a particularly preferable lithium-containing transition metal oxide positive electrode active material used in the present invention, a total of lithium compound / (transition metal compound)
V, Cr, Mn, Fe, Co, and Ni) are preferably mixed and synthesized so that the molar ratio of them is 0.3 to 2.2. Particularly preferable lithium-containing transition metal oxide positive electrode active material used in the present invention is Lix MOz (where M = Co, Mn, Ni, V,
Transition metal containing at least one selected from Fe), x
= 0.3 to 1.2 and z = 1.4 to 3).

A more preferable lithium-containing metal oxide positive electrode active material used in the present invention is Lix Co.
O ₂ , Lix NiO ₂ , Lix Coa Ni ₁ -a O ₂ , L
iz Cob V ₁ -b Oz, Lix CobFe ₁ -b O ₂ , L
ixMn ₂ O ₄ , Lix MncCo ₂ -c O ₄ , LixM
ncNi ₂ -c O ₄ , LixMncV ₂ -c Oz, LixM
ncFe ₂ -c O ₄ , a mixture of LixMn ₂ O ₄ and MnO _2, a mixture of Li ₂ xMnO ₃ and MnO ₂ , LixMn ₂
A mixture of O ₄ , Li ₂ x MnO ₃ and MnO ₂ (where x =
0.6-1.2, a = 0.1-0.9, b = 0.8-
0.98, c = 1.6 to 1.96, z = 2.01 to 5)
I can give you.

As a more preferable lithium-containing metal oxide positive electrode active material used in the present invention, LixCo
O ₂ , LixNiO ₂ , LixCoa Ni ₁ -a O ₂ , L
ixCobV ₁ -b Oz, LixCobFe ₁ -b O ₂ , L
ixMn ₂ O ₄ , LixMncCo ₂ -c O ₄ , LixM
ncNi ₂ -c O ₄ , LixMncV ₂ -c O ₄ , LixM
ncFe ₂ -c O ₄ (where x = 0.7 to 1.04, a =
0.1 to 0.9, b = 0.8 to 0.98, c = 1.6 to
1.96, z = 2.01 to 2.3).

The most preferable lithium-containing transition metal oxide positive electrode active material used in the present invention is LixCoO 2.
₂ , LixNiO ₂ , LixCoa Ni ₁ -a O ₂ , Li
xMn ₂ O ₄ , LixCob V ₁ -b Oz (where x =
0.7 to 1.04, a = 0.1 to 0.9, b = 0.9 to
0.98, z = 2.02 to 2.3). Here, the above-mentioned x value is a value before the start of charging / discharging, and increases / decreases due to charging / discharging.

In the synthesis of the positive electrode active material of the present invention, a method of chemically inserting lithium ions into the transition metal oxide is to synthesize lithium metal, lithium alloy or butyllithium with the transition metal oxide. The method is preferred.

The positive electrode active material can be synthesized by a method of mixing and firing a lithium compound and a transition metal compound or by a solution reaction, but a firing method is particularly preferable. The firing temperature may be a temperature at which a part of the mixed compound used in the present invention is decomposed and melted, for example, 250 to 200.
0 degreeC is preferable and 350-1500 degreeC is especially preferable.
The gas atmosphere for firing is not particularly limited, but is preferably in air or in a gas containing a large proportion of oxygen (for example, about 30% or more).

The average particle size of the positive electrode active material used in the present invention is not particularly limited, but is preferably 0.1 to 50 μm. A well-known crusher or classifier is used to obtain a predetermined particle size. For example, a mortar, a ball mill, a vibrating ball mill, a satellite ball mill, a planetary ball mill, a swirling airflow type jet mill, a sieve and the like are used.

For the oxide of the negative electrode active material used in the present invention
Is not particularly limited, and specific examples include W of a rutile structure.
O₂(US Pat. No. 4,198,476), LixFe.
(Fe ₂) O_FourSuch as spinel compounds (JP-A-58-2
20, 362), electrochemically synthesized Fe₂O₃of
Lithium compound (US Pat. No. 4,464,447), F
e₂O₃Lithium compound (JP-A-3-112,07)
0), Nb₂O_Five(Japanese Patent Publication No. 62-59,412, Japanese Patent Laid-Open No.
2-82,447), iron oxide, FeO, Fe₂O₃, F
e₃O_Four, Cobalt oxide, CoO, Co₂O₃, Co₃
O_Four(JP-A-3-291,862). Preferred
In particular, by inserting lithium ion, the crystal group
A transition metal oxide with a modified structure,
After that, the basic structure of the crystal was not changed by charging and discharging.
Thing (Japanese Patent Application No. 5-120908), insert lithium,
Emitting oxide containing a group IVB or VB semimetal of the periodic table
Is mentioned. The transition metal in the present invention has an element number of 2
Sc of 1 to Zn of the element symbol 30 and Y of the element number 39
From Cd with element symbol 48 and La with element number 57
Including up to Hg of the prime symbol 80. The periodic table referred to in the present invention
IVB and VB group semimetals are Ge, Sn, Pb, Sb,
It is Bi.

A preferred negative electrode of the present invention is a transition metal oxide in which the basic structure of the crystal is changed by inserting lithium ions, and the basic structure of the crystal after the change is in a state of not being changed by charge and discharge. The active material can be obtained by inserting (preferably electrochemically inserting) lithium ions into an oxide of a transition metal which may contain lithium. At that time, the lithium ion was inserted until the basic structure of the crystal was changed (the change of the basic structure of the oxide of the transition metal was confirmed by the change of the X-ray diffraction pattern), and the lithium ion was inserted. Until the lithium-containing transition metal oxide is in a state in which the changed crystal basic structure does not substantially change during charge / discharge (ie, X
Until the line diffraction pattern is substantially unchanged). In the present invention, the change in the basic structure of the crystal means a change from a certain crystal structure to a different crystal structure, or a change from a certain crystal structure to an amorphous structure (a state having no crystal structure).

The transition metal oxide used in the present invention before insertion of lithium ions (hereinafter referred to as negative electrode active material precursor)
Is prepared by mixing two or more kinds of transition metal compounds at a desired ratio, or a lithium compound and one or more kinds of transition metal compounds are mixed in a lithium compound / total transition metal compound molar ratio of 3.1 or less. It is preferable to mix them so as to be synthesized. However, transition metals include Ti, V, Mn, and C.
The transition metal contains at least one of o, Ni, Fe, Cr, Nb, and Mo. Further, the negative electrode active material precursor is preferably synthesized by mixing a lithium compound and a transition metal compound so that the molar ratio of lithium compound / total transition metal compound is 0.2 to 3.1. Here, the transition metal is the transition metal containing at least one of Ti, V, Mn, Co, Ni and Fe.

At least one of the transition metal oxides which is the precursor of the negative electrode active material of the present invention is LipMOj (provided that M
Represents at least one transition metal and at least one of the transition metals is Ti, V, Mn, Co, Ni, F
e, Cr, Nb, and Mo, p is in the range of 0 to 3.1, and j is in the range of 1.6 to 4.1).

As an example of the negative electrode active material precursor of the present invention,
Compounds, but are not limited to these compounds
Absent. For example, LiVO₃.₁, LiTiO₂.₃, CoV
O₃. ₇, LiCoVO_Four.₀, LiCo₀._FiveV₀.
_FiveO₂.₁, LiNiVO_Four.₀, Li₀. ₇₅Ni_0.5V₀._Five
O₂.₁, Li₁.₇₅Ni₀._FiveV₀._FiveO₂._Four, LiTi₀._Five
V₀._FiveO₂.₉, LiMn₀._FiveV₀._FiveO₂._Five, LiFe₀.
_FiveMn₀._FiveO₂.₁, LiCo₀. _{twenty five}V₀.₇₅O₂.₈, LiN
i₀._{twenty five}V₀.₇₅O₂.₇, LiNi₀.₀₅V₀.₉₅O₃.₁, Li
Fe₀.₀₅V₀.₉₅O₃.₁, LiMn₀.₀₅V₀.₉₅O₃.₀, L
iCa₀.₀₅V₀.₉₅O₃.₂, LiCo₀.₇₅V₀._{twenty five}O₁.₉,
LiMn₀._{twenty five}Ti₀._FiveV₀._{twenty five}O₂.₆, LiCr₀. ₀₅V₀.
₉₅O₃.₂, LiNb₀.₀₅V₀.₉₅O₃.₁, LiMo₀.₀₅V
₀.₉₅O₃.₀Is. The oxygen number is the weight of the compound before firing.
It is a value obtained from the amount and the weight after firing. Therefore, oxygen
The number is -10 to 10% of the above value due to the accuracy of the measurement method.
It needs to be added.

The above-mentioned negative electrode active material precursor is further subjected to Lip
M ₁ q ₁ M ₂ q ₂ ... Mnqn Oj (however, M ₁ M ₂ ...
Each of Mn represents the transition metal, at least one of which represents Ti, V, Mn, Co, Ni or Fe, and p is in the range of 0 to 3.1, q ₁ + q ₂
+ ... + qn = 1, n is in the range 1-10, and j is in the range 1.6-4.1). Further, in the above equation, p is 0.2 to
More preferably, it is in the range 3.1, n is in the range 1 to 4, and j is in the range 1.8 to 4.1. In particular, in the above formula, p is in the range of 0.2 to 3.1, n is in the range of 1 to 3, and j is 1.8 to
It is preferably in the range of 4.1.

As described above, the negative electrode active material precursor of the present invention is a transition metal having a valence of 5+ to 6+ stably existing (eg,
V, Cr, Nb, Mo) is preferably contained in order to obtain a high discharge capacity. From this viewpoint, as the negative electrode active material precursor of the present invention, at least V
It is particularly preferable to include

As the negative electrode active material precursor containing V,
Lip M₁q₁M₂q₂... Mnqn VqvOj (However, M is
It is a transition metal, p is in the range of 0 to 3.1, q₁
+ Q ₂+ ... + qn + qv = 1 and n is 1 to 9
Range, and j is in the range 1.3 to 4.1)
Is preferred. In addition, before the negative electrode active material containing V
The body is Lip M₁q₁M₂q₂V₁-(q₁+ q₂) Oj (However,
M is a transition metal, and p is in the range of 0.2 to 3.1.
, Q₁+ Q₂Is in the range 0-0.7, and j is
More preferably in the range of 1.3 to 4.1).
Good The negative electrode active material precursor containing V is Lip
Coq V₁-q Oj, Lip Niq V₁-q Oj (However, p
Is in the range of 0.3 to 2.2, and q is 0.02 to 0.7.
, And j is in the range 1.5 to 2.5.
Most preferably).

Examples of particularly preferable negative electrode active material precursors in the present invention include Lip CoVO ₄ and Lip NiVO ₄ (where p is in the range of 0.3 to 2.2). Here, the above p value is a value before the start of charging / discharging, and increases / decreases due to charging / discharging. Further, the negative electrode active material has the same precursor composition formula with an increased content of lithium, and has an X-ray diffraction pattern substantially different from that of the negative electrode active material precursor. The general formula shown in the present invention (eg, LipM
In Oj), the total number of transition metals M is 1. Therefore, when there are a plurality of transition metals or in a crystallographic composition formula, they may be multiplied by an integer.

The preferred negative electrode active material of the present invention is one prepared by inserting lithium ions into the above negative electrode active material precursor.
Therefore, the Lip of the transition metal oxide which may contain lithium as the negative electrode active material precursor is Lix. That is, x is generally in the range of 0.17 to 11.25 (the increase xp of lithium due to lithium ion insertion is generally in the range of 0.17 to 8.15). For example, a more preferable negative electrode active material of the present invention obtained by inserting lithium ions into Lip MOj of the above preferable negative electrode active material precursor is LixMOj (where M represents at least one transition metal and At least one is selected from Ti, V, Mn, Co, Fe, Ni, Nb and Mo, and p is in the range of 0 to 3.1,
x is in the range of 0.17 to 11.25 and j is in the range of 1.6 to 4.1)). x is preferably in the range of 0.26 to 10.2, and further x
Is preferably in the range of 0.34 to 9.3. Further, a preferable negative electrode active material is Lix Mq V ₁ -q Oj (where M represents a transition metal, p is in the range of 0 to 3.1, and x is 0.
In the range of 17 to 8.15, q in the range of 0 to 0.7, and j in the range of 1.3 to 4.1)). Is. x is preferably in the above range.

The preferred negative electrode active material of the present invention can be obtained by inserting lithium ions into a negative electrode active material precursor of a transition metal oxide and / or a lithium-containing transition metal oxide as follows. For example, a method of reacting with lithium metal, a lithium alloy, butyl lithium, or the like, or a method of 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 use a lithium-containing transition metal oxide as a negative electrode active material precursor and electrochemically insert lithium ions into the transition metal oxide. As a method of electrochemically inserting lithium ions, a target lithium-containing transition metal oxide (a negative electrode active material precursor in the present invention) is included as a positive electrode active material, and lithium metal and a lithium salt are included as a negative electrode active material. It can be obtained by discharging a redox system composed of a non-aqueous electrolyte (for example, an open system (electrolysis) or a closed system (battery)). Furthermore, a redox system (for example, an open system) composed of 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 a non-aqueous electrolyte containing a lithium salt. A method obtained by charging (electrolysis) or closed system (battery)) is preferable.

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.
And 54-938 mAh (2-35 mmol equivalent) is the most preferable.

The negative electrode active material thus obtained is one in which the basic structure of the crystal of this precursor is changed, and this change is preferably from the diffraction angle (2θ) 5 of the X-ray diffraction pattern by CuKα line. This is a change confirmed by changing the intensity of the X-ray diffraction maximum peak in the range of 70 degrees to ⅕ or less. Particularly, 1/10 or less is preferable, and 1/20 or less is most preferable. The intensity 0 here means that substantially all of the precursor of the negative electrode active material has changed to a negative electrode active material capable of charging and discharging, and specifically, noise of the X-ray diffraction pattern (baseline ) Level. Furthermore, it is preferable that at least one of the peaks other than the main peak disappears or a new peak is expressed.

The negative electrode active material thus obtained is generally a lithium-containing transition metal oxide, and the crystal thereof has a diffraction angle (2θ) of 5 to 70 degrees in an X-ray diffraction pattern by CuKα ray. It has a basic structure characterized by the intensity of all X-ray diffraction peaks within the range of 20 to 1000 cps. The peak intensity is preferably 20 to 800 cps, and further 20 to 5
00 cps is preferred, and 20-400 cps is most preferred. As the measurement conditions for the above X-ray diffraction, 40 k
V, 120 mA, scan speed = 32 ° / min. As a standard compound, the signal intensity of the main peak of LiCoO ₂ 2θ = 18.9 ° (4.691 Å) was 7990 cps. (L
iCoO ₂ Synthesis Method: Li ₂ CO ₃ and CoCO ₃ are Li
/ Co = 1 (molar ratio) is mixed in a mortar, transferred to a magnetic crucible, left at 130 ° C for 1 hour, and then baked in air at 900 ° C for 6 hours. After cooling at 2 ° C./min, the mixture is ground in a mortar until the average particle size is about 7.5 μm in median diameter. The crystal form of the negative electrode active material is not a layered structure, a spinel structure or a rutile structure, but one having another crystal structure or one having no crystal structure.

Furthermore, the phrase "the negative electrode active material does not substantially change the X-ray diffraction pattern during charge and discharge" in the present invention means that the crystalline or amorphous material expands or contracts due to the absorption and desorption of lithium ions. As a result, the bond length and the morphology of the particles change, but the basic crystalline or amorphous structure does not change. Specifically, during charging / discharging, the variation range of the lattice (plane) spacing obtained from the peak value of the X-ray diffraction method is preferably −0.1 to 0.1 angstrom, and further −0.05 to 0.05. Angstrom is preferred. Further, the peak intensity ratio and the half width may vary.

As described above, the X-ray diffraction pattern of the preferred negative electrode active material in which the lithium ions of the present invention are inserted does not substantially change even after repeated charging and discharging. For example, LiCoVO _4, which is a negative electrode active material precursor, is V ₅ ⁺ (Li ⁺
The inverse spinel structure represented by Co ₂ ⁺ ) O ₄
When lithium ions are electrochemically inserted into this oxide, the crystal structure changes to an unknown crystal structure or an amorphous structure giving a broad peak around 2 angstroms. This once-changed crystal structure or amorphous structure does not substantially change even if charging and discharging are repeated. This means that, as described in JP-A-58-220362, "If too many lithium ions are inserted into the spinel structure, the spinel structure is destroyed and an unknown compound is formed, which is not preferable as an active material of a secondary battery. , Which is the opposite of the conventional knowledge. Since the compound having this new structure has a low redox potential, it can be a negative electrode active material.

In the present invention, "the positive electrode active material and the negative electrode active material have different composition formulas" means the following: Different combinations of metal elements, and 2. Positive electrode active material Liy Cob V1-b Oz and negative electrode active material L
The example ix Coq V1-q Oj means that the values of y and x, b and q, and z and j are not equal at the same time. In particular, this means that b and q and z and j are not equal at the same time. The positive electrode active material and the negative electrode active material used in the present invention are preferably combined with compounds having different standard redox potentials.

The negative electrode active material precursor of the present invention can be synthesized by a method of mixing and firing a lithium compound and a transition metal compound or a solution reaction, but a firing method is particularly preferable. The firing temperature may be a temperature at which a part of the mixed compound used in the present invention is decomposed and melted, and for example, 25
0-2000 degreeC is preferable and 350-1500 degreeC is especially preferable. The gas atmosphere for firing is not particularly limited, but a gas in air or a gas having a low oxygen ratio (for example, about 10
% Or less) or an inert gas (nitrogen gas, argon gas) is preferable. Further, for example, when a lithium compound, a vanadium compound or a cobalt compound is mixed and fired, LiVO ₃ or Li ₃ VO ₄ may be produced. As described above, a compound having a low activity as a negative electrode active material precursor may be included in the synthesis process. Such a compound may be contained as it is, but may be removed if desired.

The negative electrode active material precursor of the present invention is 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, monovalent to 6
A valent transition metal oxide, the same transition metal salt, or the same transition metal complex salt is used.

Preferred lithium compounds that can be used in the present invention include lithium oxide, lithium hydroxide, lithium carbonate, lithium nitrate, lithium sulfate, lithium sulfite, lithium phosphate, lithium tetraborate, lithium chlorate and perchloric acid. Lithium, lithium thiocyanate,
Lithium formate, lithium acetate, lithium oxalate, lithium citrate, lithium lactate, lithium tartrate, lithium pyruvate, lithium trifluoromethanesulfonate, lithium tetraborate, lithium hexafluorophosphate, lithium fluoride, lithium chloride, bromide Examples thereof include lithium and lithium iodide.

Preferred transition metal compounds that can be used in the present invention include TiO ₂ , lithium titanate,
Acetylacetonato titanyl, titanium tetrachloride, titanium tetraiodide, titanyl ammonium oxalate, VOd (d = 2 to
2.5 d = 2.5 compound is vanadium pentoxide), V
Od lithium compound, vanadium hydroxide, ammonium metavanadate, ammonium orthovanadate, ammonium pyrovanadate, vanadium oxosulfate, vanadium oxytrichloride, vanadium tetrachloride, lithium chromate, ammonium chromate, cobalt chromate, chromium acetylacetoacetate Naates, 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, formic acid. Manganese, manganese acetate, manganese oxalate, manganese citrate, manganese lactate, manganese tartrate, manganese stearate, manganese fluoride, manganese chloride, manganese bromide, manganese iodide, manganese acetyl Acetonate, 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 ferric acid (2,3 valent),
Iron oxalate (2,3 valent), ammonium iron oxalate (2,3)
Price),

CoO, Co ₂ O ₃ , Co ₃ O ₄ , LiC
oO 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, hexaammine cobalt 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, nickel fluoride, nickel chloride, nickel bromide, nickel iodide, nickel formate, nickel acetate, nickel acetylacetonate, copper oxide (divalent), 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, penta Niobium iodide, niobium monoxide, niobium dioxide, niobium trioxide, niobium pentoxide, niobium oxalate, niobium methoxide, niobium ethoxide, niobium propoxide, niobium oxide Kishido, lithium niobate,
MoO ₃ , MoO ₂ , LiMo ₂ O ₄ , molybdenum pentachloride, ammonium molybdate, lithium molybdate, ammonium molybdophosphate, molybdenum acetylacetonate oxide, WO ₂ , WO ₃ , tungstic acid, ammonium tungstate, ammonium tungstophosphate. Can be mentioned.

Particularly preferred which can be used in the present invention
As a transition metal compound, TiO 2 ₂, Titanyl oxalate
Limonium, VOd (d = 2-2.5), VOd
Um compounds, ammonium metavanadate, MnO₂,
Mn₂O₃, Manganese hydroxide, manganese carbonate, man nitrate
Cancer, ammonium manganese sulfate, manganese acetate, oxalic acid
Manganese, manganese citrate, iron oxide (2,3 valent), four
Iron trioxide, iron hydroxide (2,3 valent), iron acetate (2,3)
Value), iron citrate (2,3 value), iron citrate ammoniu
(2,3 values), iron oxalate (2,3 values), iron oxalate ammonium
Um (2,3 valence), CoO, Co₂O₃, Co₃O_Four,
LiCoO₂, Cobalt carbonate, basic cobalt carbonate, water
Cobalt oxide, cobalt oxalate, cobalt acetate, nickel oxide
Gel, nickel hydroxide, nickel carbonate, basic nitric carbonate
Kell, nickel sulfate, nickel nitrate, nickel acetate, acid
Copper (1 and 2), copper hydroxide, copper acetate, copper citrate, M
oO₃, MoO₂, LiMo₂O_Four, WO₂, WO₃To
Can be mentioned.

Particularly preferred which can be used in the present invention
As a combination of a lithium compound and a transition metal compound, an acid
Lithium fluoride, lithium hydroxide, lithium carbonate, lithium acetate
Lithium of um and VOd (d = 2-2.5), VOd
Compound, ammonium metavanadate, MnO₂, Mn₂
O₃, Manganese hydroxide, manganese carbonate, manganese nitrate,
Iron oxide (2,3 valence), triiron tetraoxide, iron hydroxide (2,3)
Valent) iron acetate (2,3 valent), iron citrate (2,3 valent),
Ammonium iron enoate (2,3 valent), iron oxalate (2,3)
Valence), ammonium iron oxalate (2,3 valence), CoO, Co
₂O₃, Co₃O_Four, LiCoO₂, Cobalt carbonate, salt
Basic cobalt carbonate, cobalt hydroxide, cobalt sulfate, glass
Cobalt acid, nickel oxide, nickel hydroxide, nickel carbonate
Kell, basic nickel carbonate, nickel sulfate, nickel nitrate
, Nickel acetate, MoO₃, MoO ₂, LiMo₂O
_Four, WO₃Can be mentioned.

In addition to lithium compounds and transition metal compounds,
In general, compounds that enhance ionic conductivity, such as Ca ₂ ⁺ (eg, calcium carbonate, calcium chloride, calcium oxide, calcium hydroxide, calcium sulfate, calcium nitrate, calcium acetate, calcium oxalate, calcium citrate, calcium phosphate). Alternatively, P, B, S
An amorphous former such as i (eg, P ₂ O ₅ , Li
₃ PO ₄ , H ₃ BO ₃ , SiO ₂ etc.) and the mixture may be fired. Further, alkali metal ions such as Na, K and Mg and / or Sn, Al, Ga, Ge, Ce,
You may mix with a compound containing In, Bi, etc. (for example, each oxide, hydroxide, carbonate, nitrate, etc.), and bake. Among them, calcium carbonate or P ₂ O ₅
It is preferable to mix with and fire. The addition amount is not particularly limited, but 0.2 to 10 mol% is preferable.

A transition metal oxide used in the present invention in which the basic structure of the crystal is changed by inserting lithium ions, and the negative electrode active state in which the basic structure of the crystal after the change is not changed by charge and discharge. The average particle size of the material is not particularly limited, but is preferably 0.03 to 50 μm. A known crusher or classifier can be used to obtain a predetermined particle size. Examples thereof include a mortar, a ball mill, a vibrating ball mill, a satellite ball mill, a swirling airflow type jet mill and a sieve.

The chemical formula of the compound obtained by the above-mentioned calcination was calculated from the weight difference of the powder before and after calcination as a simple method, and as a simple method.

Both the positive electrode active material and the negative electrode active material used in the present invention obtained as described above are considered to be compounds that occlude and release lithium ions by charging and discharging, and change the valence of the transition metal. . Therefore, the negative electrode active material of the present invention is a negative electrode active material having a concept that is fundamentally different from the method of depositing and dissolving lithium by charging and discharging, like a metal negative electrode active material such as lithium metal or lithium alloy. Also,
Similarly, when compared to carbonaceous compounds, carbon is not a compound that changes its valence clearly, and also has high conductivity,
It is a compound that easily deposits lithium metal during charging. Therefore, the negative electrode active material of the present invention is a negative electrode active material whose concept is fundamentally different from that of lithium metal or carbonaceous material.

The preferred precursors of lithium-inserting / releasing oxides containing Group IVB and VB metalloids of the present invention will be described below. For example, α-PbO structure SnO
It was discovered that the rutile structure SnO ₂ itself does not work as a negative electrode active material of a secondary battery, but if lithium is continuously inserted into them, the crystal structure changes and it can reversibly work as a negative electrode active material of a secondary battery. did. That is, the charging / discharging efficiency in the first cycle is as low as about 80% or about 60%. Therefore, in the present invention, for example, the α-PbO structure S of the starting material is used.
compounds such as nO and rutile structure SnO ₂ ,
The compound before lithium is inserted will be referred to as "a precursor (2) of the negative electrode active material".

Negative electrode active material or precursor thereof referred to in the present invention
As a specific example of the body (2), Lis Z ₁tOu (In the formula, Z₁
Is a small amount selected from Si, Ge, Sn, Pb, Bi and Sb.
At least one kind, s = 0.1-8, t = 1-7, u = 1-
Represents the number 20. ), Lis SnZ₂Ou (in the formula, Z
₂Is at least one selected from In and Mg, s = 0.
1 to 8, t = 1 to 7, and u = 1 to 20 are represented. ),
GeO, GeO₂, SnO, SnO₂, PbO, PbO
₂, Pb₂O₃, Pb₃O_Four, Sb₂O₃, Sb
₂O_Four, Sb₂O_Five, Bi₂O₃, Bi₂O_Four, Bi₂
O_FiveOr non-stoichiometric compounds of these oxides
To be Negative electrode active material or precursor thereof referred to in the present invention
Among the specific examples of (2), Lis Z₁tOu (In the formula, Z
₁Is selected from Si, Ge, Sn, Pb, Bi, Sb
At least one kind, s = 0.1-8, t = 1-7, u = 1
Represents a number from -20. ), Lis SnZ₂tOu (where
Z₂Is at least one selected from In and Mg, s =
Show numbers from 0.1 to 8, t = 1 to 7, u = 1 to 20
You ), SnO, SnO₂, GeO, GeO₂Is preferred
In particular, Lis SnOv (in the formula, s = 0.1 to 8, v =
Represents a number from 1 to 6. ), SnO, SnO₂Is preferred
Yes. Furthermore, Lis SnOv (in the formula, s = 0.1 to 8,
v represents a number from 1 to 6. ), Α-PbO structure SnO,
Rutile structure SnO₂, GeO, Rutile structure GeO₂Is good
Most preferably, Lis SnOv (in the formula, s = 0.1 to
8 represents the number v = 1 to 6. ), Α-PbO structure Sn
O, rutile structure SnO₂Is preferred.

Lis Z ₁ tOu (where Z is Si, Ge,
At least one selected from Sn, Pb, Bi, Sb,
The numbers s = 0.1 to 8, t = 1 to 7, and u = 1 to 20 are represented. ), Lis SnZ ₂ tOu (wherein Z ₂ is In, Mg
At least one selected from s = 0.1 to 8 and t = 1
-7, u = 1 to 20 is represented. ), Lis SnOv
(In the formula, s = 0.1 to 8 and v = 1 to 6 are represented.)
The valences of Z ₁ , Z ₂ and Sn in are not particularly limited, and may be a single valence or a mixture of valences. Further, the amount of lithium in these lithium composite oxides can be continuously changed, and at that time, a mixture of the above compound examples or a single-phase compound can be obtained, but in the present invention, either a mixture or a single-phase compound may be used. If the lithium amount is small also, and the compound examples, lithium-free oxides (e.g. Sn O, Sn O _2, etc.) they may have a mixture of, it is effective in the mixture in the present invention .

Lis Z₁tOu (In the formula, Z is Si, Ge,
At least one selected from Sn, Pb, Bi, Sb,
Show the numbers s = 0.1-8, t = 1-7, u = 1-20
You ) Specific examples of the lithium composite oxide represented by
Is Li_FourGe₉O₂₀, Li₆Ge₈O₁₉, Li_FourGe
_FiveO₁₂, Li₆Ge₂O₇, Α-Li_FourGe O_Four, Li_FourG
eO_Four, Β-Li₈GeO₆, Li₂Ge₇O₁₅, Li₂GeO
₃, Li₂Ge_FourO₉, Li₂SnO₃, Li₈SnO₆, Li₂
PbO₃, Β-Li₂PbO₃, Li₈PbO₆, Li_FourPb
O_Four, Li₇SbO₆, LiSbO₃, Li₃SbO_Four, L
i₃BiO_Four, Li₇BiO₆, Li_FiveBiO_Five, LiBiO
₂, Li_FourBi₆O₁₁, Or these non-stoichiometric compounds
Can be mentioned. LisSnZ₂tOu (In the formula, Z₂Is In,
At least one selected from Mg, s = 0.1-8, t
= 1 to 7, u = 1 to 20. ) Represented by
Specific examples of the thiium composite oxide include Li_FourMgSn
₂O₇, Li₂MgSn₂O₆, Li₂MgSn₃O₆, Li₂Mg
₃SnO₆, Li_FourMg₂SnO₆, Or these non-quantities
Compounds and the like. LisSnOv (where s =
It represents the numbers of 0.1 to 8 and v = 1 to 6. ) Represented by
Specific examples of the thiium composite oxide include Li₀.₁Sn
O₂.₀₅, Li₀._FiveSnO₂. _{twenty five}, LiSnO₂._Five, Li₁._FiveS
nO_2.75, Li₂SnO₃, Li₃SnO₃._Five, Li_FourSnO
_Four, Li_FiveSnO_Four._Five, Li₆SnO_Five, Li₇SnO_Five._Five,
Li₈SnO₆, Li_0.1SnO₁.₀₅, Li₀._FiveSn
O₁._{twenty five}, LiSnO₁._Five, Li₁._FiveSnO₁.₇₅, Li₂Sn
O₂, Li₃SnO₂._Five, Li_FourSnO₃, Li_FourSn
O₃._Five, Li₆SnO_Four, Li₇SnO_Four._Five, Li₈Sn
O_Five, Or these non-stoichiometric compounds.

Various compounds can be contained in the negative electrode active material precursor (2) of the present invention. For example, transition metals (elements of the 4th, 5th and 6th periods of the periodic table belonging to groups IIIA to IB), elements of the group IIIB of the periodic table, alkali metals (IA of the periodic table) , Element IIA) and P, Cl, Br, I, F. For example, SnO ₂ may contain Si as a homologous element as a dopant of various compounds (for example, compounds of Sb, In, and Nb) that increase electron conductivity. The amount of the compound added is preferably 0 to 20 mol%.

As a method for synthesizing the precursor (2) of the negative electrode active material, SnO ₂ is a Sn compound, for example, stannic chloride,
An aqueous solution of stannic bromide, stannic sulfate, stannic nitrate and an alkali hydroxide, such as lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, ammonium hydroxide, etc. The aqueous solutions are mixed to precipitate stannic hydroxide, which is washed and separated. After the stannic hydroxide is almost dried, it is heated in air, in a gas rich in oxygen or in a gas low in oxygen in an amount of 250 to 20.
Bake at 00 ° C. Alternatively, the stannic hydroxide can be baked as it is and then washed. The average size of the primary particles is 0.01 μm to 1 as measured by a scanning electron microscope.
μm is preferred. Particularly, 0.02 μm to 0.2 μm is preferable. The average size of secondary particles is 0.1 to 60 μm.
Is preferred. Similarly, with SnO, an aqueous solution of stannous chloride, stannous bromide, stannous sulfate, and stannous nitrate and an alkali hydroxide such as lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide are used. , Magnesium hydroxide,
Mix an aqueous solution such as ammonium hydroxide and boil. In addition, stannous oxalate was added in a gas containing little oxygen to 250
Bake at ~ 1000 ° C. Its average particle size is 0.
1-60 micrometers is preferable. Other oxides are SnO ₂
Like SnO and SnO, it can be synthesized by a well-known method. Its preferable physical properties are the same as those of SnO described above. A well-known crusher or classifier is used to obtain a predetermined particle size. For example, a mortar, a ball mill, a vibrating ball mill, a satellite ball mill, a planetary ball mill, a swirling airflow type jet mill, a sieve and the like are used.

The negative electrode active material used in the present invention can be obtained by chemically inserting lithium into its precursor (2). For example, a method of reacting with lithium metal, a lithium alloy, butyl lithium, or the like, or electrochemically inserting lithium is preferable. In the present invention, it is particularly preferable to electrochemically insert lithium into the oxide that is the precursor (2). As a method of electrochemically inserting lithium ions, a target oxide (a negative electrode active material precursor (2) referred to in the present invention) as a positive electrode active material, and a non-metal containing lithium metal or a lithium salt as a negative electrode active material. It can be obtained by discharging a redox system composed of a water electrolyte (for example, an open system (electrolysis) or a closed system (battery)).
Further, as another embodiment example, a redox system (for example, an open system) including a lithium-containing transition metal oxide as a positive electrode active material, a negative electrode active material precursor (2) as a negative electrode active material, and a non-aqueous electrolyte containing a lithium salt is used. The method obtained by charging (electrolysis) or closed system (battery)) is most preferable.

The insertion amount of lithium is not particularly limited, but the equivalent amount of ordinary lithium insertion is 3 to 10 equivalents, and the ratio of the amount used with the positive electrode active material is determined according to this equivalent amount. The usage rate based on this equivalent is 0.5 to
It is preferable to use it by multiplying it by a factor of 2. When the lithium source is other than the positive electrode active material (for example, lithium metal, alloy, butyl lithium, etc.), the amount of the positive electrode active material used is determined according to the lithium release equivalent of the negative electrode active material. Also at this time, it is preferable to multiply the usage ratio based on this equivalent by a coefficient of 0.5 to 2 times.

It was discovered that when the oxide of the present invention was used as the precursor (2) of the negative electrode active material, "each metal (alloy with lithium) was not reduced even when lithium was inserted." (1) Precipitation of metal by transmission electron microscope observation (especially dendrite precipitation)
, (2) the potential of lithium insertion / release via the metal is different from that of the oxide, and (3)
It can be inferred from the fact that in SnO, the loss of release due to the insertion of lithium was about 1 equivalent, which does not match the loss of 2 equivalents when metal tin is generated. The potential of the oxide is similar to that of currently used calcined carbonaceous compounds, and it is presumed that, like calcined carbonaceous compounds, it is in a state where it is neither a simple ionic bond nor a simple metal bond. It Therefore, it can be said that the present invention is an invention which is clearly different from the conventional lithium alloy.

The oxide (precursor (2)) of the present invention has a crystal structure, but as lithium is inserted, the crystallinity decreases and the crystallinity changes. Therefore, the structure in which reversible redox is performed as the negative electrode active material is presumed to be a compound having high amorphousness. Therefore, the oxide (precursor (2)) of the present invention may have a crystalline structure, an amorphous structure, or a mixed structure thereof.

As the negative electrode active material that can be used in combination with the present invention, lithium metal, lithium alloy (Al, A
1-Mn (U.S. Pat. No. 4,820,599), Al-
It absorbs Mg (JP-A-57-98977), Al-Sn (JP-A-63-6,742), Al-In, Al-Cd (JP-A-1-144,573), lithium ion or lithium metal. A calcined carbonaceous compound that can be released (for example, JP-A-58-209,864 and 61-214,
417, the same 62-88, 269, the same 62-216,
170, same 63-13, 282, same 63-24, 5
55, the same 63-121, 247, the same 63-121,
257, 63-155, 568, 63-276,
873, 63-314, 821, JP-A-1-20.
4,361, 1-221,859, 1-27
4,360). The purpose of using the lithium metal or lithium alloy together is to insert lithium in the battery, and does not utilize the dissolution / precipitation reaction of lithium metal or the like as the battery reaction.

A conductive agent, a binder, a filler or 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. In addition, when the precursor of the active material is made to have electronic conductivity like SnO ₂ is doped with Sb, the amount of the conductive agent can be reduced. For example, addition of 0 to 10% by weight is preferable.

The binder is usually starch, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, diacetyl cellulose, polyvinyl chloride, polyvinyl pyrrolidone,
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 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, the electrolytic solution may contain carbon dioxide gas in order to have suitability for high temperature storage. (JP-A-59-1
34,567)

The mixture for 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.

As a method for adjusting the negative electrode mixture or the positive electrode mixture, a powder of an active material, a conductive agent, a binder or the like is preferably dry, or a method of adding water or an organic solvent and wet mixing. Further, the binder may be a solution in advance or a dispersion (latex) one. Preferred examples of the mixing device include a mortar, a mixer, a homogenizer, a dissolver, a sand mill, a paint shaker, a kneader and a dyno mill.

The shape of the battery can be any of coins, buttons, sheets, cylinders, corners and the like. When the shape of the battery is a coin or a button, the mixture of the positive electrode active material and the negative electrode active material is used by being compressed into a pellet shape. The thickness and diameter of the pellet are determined by the size of the battery. Further, when the shape of the battery is a sheet, a cylinder, or a corner, the mixture of the positive electrode active material and the negative electrode active material is applied (coated) on the current collector, dried and compressed, and is mainly used. As a coating method, a general method can be used. Examples thereof include a reverse roll method, a direct roll method, a blade method, a knife method, an extrusion method, a curtain method, a gravure method, a bar method, a dip method and a squeeze method. The blade method, knife method and extrusion method are preferred. The coating is preferably carried out at a speed of 0.1 to 100 m / min. At this time, a good surface condition of the coating layer can be obtained by selecting the above-mentioned coating method according to the solution physical properties and drying properties of the mixture. The thickness, length and width of the coating layer are determined by the size of the battery, but the thickness of the coating layer is particularly preferably 1 to 2000 μm in a compressed state after drying.

As a method for drying or dehydrating the pellets or sheets, a generally adopted method can be used. In particular, it is preferable to use hot air, vacuum, infrared rays, far infrared rays, electron beams, and low humidity air alone or in combination. The temperature is preferably in the range of 80 to 350 ° C, particularly 10
The range of 0 to 250 ° C. is preferable. The water content of the whole battery is preferably 2000 ppm or less, and the content of each of the positive electrode mixture, the negative electrode mixture and the electrolyte is preferably 500 ppm or less from the viewpoint of cycleability. As a pellet or sheet pressing method, a generally adopted method can be used, but a die pressing method or a calendar pressing method is particularly preferable. The pressing pressure is not particularly limited, but is 0.2 to 3 t /
cm ² is preferred. The press speed of the calendar press method is preferably 0.1 to 50 m / min. 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. Other than safety valve,
Various conventionally known safety elements may be provided. For example, a fuse, a bimetal, a PTC element or the like is used as the overcurrent prevention element. In addition to the safety valve, a method of making a notch in the battery can, a method of cracking a gasket, or a method of cracking a sealing plate can be used as a measure for increasing the internal pressure of the battery can. Further, the charger may be provided with a circuit incorporating measures against overcharge and overdischarge.

The total amount of the electrolytic solution may be injected once, but it is preferable to perform the injection in two or more stages. In the case of injecting in two or more stages, even if each solution has the same composition, different compositions (for example, after injecting a non-aqueous solvent or a solution of a lithium salt dissolved in a non-aqueous solvent, a non-aqueous solvent having a higher viscosity than the solvent) are used. A solution of a lithium salt dissolved in a solvent or a non-aqueous solvent may be injected). In addition, the battery can is depressurized (preferably 500 to 1) in order to shorten the injection time of the electrolytic solution.
Torr, more preferably 400 to 10 Torr), or centrifugal force or ultrasonic waves may be applied to the battery can.

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. Caps, cans,
As a welding method for the sheet and the lead plate, a known method (eg, DC or AC electric welding, laser welding, ultrasonic welding) can be used. As the sealing agent for sealing, a conventionally known compound or mixture such as asphalt can be used.

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 cycle performance is substantially improved. A voltage that can be maintained is preferable.

The application of the non-aqueous secondary battery of the present invention is not particularly limited. For example, when the non-aqueous secondary battery is installed in an electronic device, it is a color notebook computer, a black and white notebook computer, a pen input computer, a pocket (palmtop) computer, a notebook. Type word processor, pocket word processor, e-book player, mobile phone, cordless phone handset, pager, handy terminal, mobile fax, mobile copy, mobile printer, headphone stereo, video movie, LCD TV, handy cleaner, portable CD, mini disk, Electric shaver, electronic translator, car phone,
There are transceivers, power tools, electronic organizers, calculators, memory cards, tape recorders, radios, backup power supplies, memory cards, etc. Other consumer products such as automobiles, electric vehicles, motors, lighting equipment, toys,
Game equipment, road conditioners, irons, watches, strobes, cameras, photosensitive material packaging units with shooting functions, medical equipment (pacemakers, hearing aids, shoulder scrubbers, etc.) and the like. Furthermore, it can be used for various military purposes and for space. It can also be combined with a solar cell.

[0081]

EXAMPLES The present invention will be described in more detail with reference to the following specific examples.
As will be explained, the present invention can be implemented unless it goes beyond the gist of the invention.
It is not limited to the example. SnO, LiCoO₂Is
A commercially available product was used. SnO₂Synthesis method: SnCl_FourAnd NaOH to Sn (O
H)_FourWas synthesized and calcined in air at 400 ° C for 4 hours to give S
nO₂Is synthesized and crushed in a mortar. The average primary particle size is
About 0.05 μm (rutile structure) Li₂SnO₃Synthesis method: Empty lithium carbonate and tin dioxide
Synthesized by firing at 1000 ° C for 12 hours in air
Crush with LiCoVO_FourSynthesis method of lithium carbonate and cobalt oxide
And vanadium pentoxide in air at 750 ° C for 12 hours
Then, synthesize and crush in a mortar LiCo_0.95V_0.05O_2.07Synthesis method of: Li₂CO₃, C
oCO₃, NH_FourVO ₃And bake at 900 ° C for 6 hours
Combining and crushing in a mortar

Example 1 82% by weight of LiCoO ₂ (a) as a positive electrode active material, 8% by weight of flake graphite as a conductive agent, 4% by weight of acetylene black, and 6% by weight of polytetrafluoroethylene as a binder. A positive electrode pellet (13 mmΦ, an amount corresponding to the lithium insertion capacity of the negative electrode active material precursor was used. The charge capacity of LiCoO ₂ was 170 mAh / g) obtained by compression-molding the mixture mixed at the mixing ratio of. It was used as a positive electrode material after dehydration (150 ° C., 3 hours) with a far infrared heater in a box (dew point −40 to −70 ° C., dry air). SnO (A) was used as a negative electrode active material precursor in an amount of 80% by weight, scaly graphite was used as a conductive agent in an amount of 11% by weight, acetylene black was used in an amount of 3% by weight, and polyvinylidene fluoride was used as a binder in an amount of 6% by weight. The negative electrode pellet (13 mmΦ, 22.5 mg) obtained by compression-molding the mixed mixture was dehydrated with a far infrared heater in the same dry box as above (1
It was used as a negative electrode material at 50 ° C. for 3 hours. The current collector is
An 80 μm thick SUS316 net was welded to the coin can for both the positive and negative electrode cans. 20 electrolytes shown in Table 1
0 μl was used, and further, a microporous polypropylene sheet and a polypropylene non-woven fabric were used as a separator, and the electrolyte was impregnated into the non-woven fabric. Then, a coin type lithium battery as shown in FIG. 1 was produced in the same dry box as above.

[0083]

[Table 1]

In FIG. 1, the negative electrode material mixture pellets 2 are enclosed between the negative electrode sealing plate 1 and the separator 3, and the current collector 5
The positive electrode material mixture pellets 4 are enclosed between the positive electrode case 6 and the separator 3, and the gasket 7 is provided between the outer edge of the negative electrode sealing plate 1 and the outer edge of the positive electrode case 6. Keep this lithium battery at 22 ℃, 0.7
A charge / discharge test was performed in the range of 4.3 to 2.7 V at a constant current density of 5 mA / cm ² . All tests started with charging. ) Further, at -10 ° C, the same test as at 22 ° C was conducted.

The evaluation results are shown in Table 2. Table 2 (Table 3, Table 4
The same applies to the abbreviations shown below.
(A) First discharge capacity (mAh per 1 g of the negative electrode active material precursor), (a) Discharge average voltage (V), (c) Cycle property ((10th discharge capacity-first discharge capacity ) /
First discharge capacity), (d) First discharge capacity (mAh per 1 ml of cylindrical battery volume), and above (a) (b)
(C) and (D) were performed at 22 ° C. (E) First discharge capacity at −10 ° C. (mAh per 1 g of negative electrode active material).

[0086]

[Table 2]

Example 2 A battery was prepared in the same manner as in Example 1 except that LiCo _0.95 V _0.05 O _2.07 (b) was used as the positive electrode active material. The results are shown in Table 3.

Example 3 Instead of the negative electrode active material precursor SnO (A), SnO
₂ (B), Li ₂ SnO ₃ (C), LiCoVO
_A battery was made in the same manner as in Example 1 except that ₄ (D) was used. The results are shown in Table 3.

Comparative Example 1 A battery was prepared in the same manner as in Example 1 except that the electrolytes shown below were used. The results are shown in Table 3. 16. PC + DME (volume ratio 1: 1) 1M LiBF ₄ 17. EC + acetonitrile (volume ratio 1: 1) 1M LiBF ₄ 18. EC + dimethylformamide (volume ratio 1: 1) 1M LiBF ₄ 19. EC + DEC (volume ratio 1: 1) 1M LiBF ₄

[0090]

[Table 3]

Example 4 SnO (A) was used as a precursor of the negative electrode active material, and each was mixed at a ratio of 86% by weight, flake graphite 6% by weight, and acetylene black 3% by weight, and further a binder. As an additive, 4% by weight of an aqueous dispersion of styrene-butadiene rubber and 1% by weight of carboxymethyl cellulose were added and kneaded with water as a medium to prepare a slurry. The slurry to a thickness of 1
Both sides of a copper foil having a thickness of 8 μm were applied by an extrusion method, dried, compression-molded by a calender press, and cut into a predetermined width and length to prepare a strip-shaped negative electrode sheet.
The thickness of the negative electrode sheet was 124 μm. 87% by weight of LiCoO ₂ (a) was used as a positive electrode active material, and flaky graphite 6
% By weight, 3% by weight of acetylene black, 3% by weight of an aqueous dispersion of polytetrafluoroethylene and 1% by weight of sodium polyacrylate as a binder, and kneaded with water as a medium to obtain a slurry having a thickness of 20 μm. Apply to both sides of aluminum foil in the same manner as above, dry, press,
Disconnected. Then, a 220 μm band-shaped positive electrode sheet was produced. After spot welding nickel and aluminum lead plates to the ends of the negative electrode sheet and the positive electrode sheet, respectively, 150 in dry air with a dew point of −40 ° C. or lower.
It was dehydrated and dried at ℃ for 2 hours. Further, the dehydrated and dried positive electrode sheet (8), the microporous polypropylene film separator (Celgard 2400), the dehydrated and dried negative electrode sheet (9) and the separator (10) were laminated in this order, and wound in a spiral shape with a winding machine. Turned

The wound body was housed in a bottomed cylindrical battery can (11) made of iron and plated with nickel and also serving as a negative electrode terminal. Further, the electrolyte shown in Table 1 was injected into the battery can as the electrolyte. A battery lid (12) having a positive electrode terminal was caulked via a gasket (13) to produce a cylindrical battery. The positive electrode terminal (12) was connected to the positive electrode sheet (8), and the battery can (11) was connected to the negative electrode sheet (9) by a lead terminal in advance. FIG. 2 shows a cross section of the cylindrical battery.
Incidentally, (14) is a safety valve. Charge / discharge conditions are 4.3
˜2.7 V and 1 mA / cm ² . The results are shown in Table 4.
Shown in.

[0093]

[Table 4]

As a result of Examples 1 to 4 and Comparative Example 1, the compounds of the present invention had a high discharge voltage and a long charge / discharge cycle,
It was shown that the discharge capacity was large. The pellet specific gravity of the lithium-containing transition metal oxide, which is the negative electrode active material of the present invention, is 2.5 to 3.5, and that of the calcined carbonaceous material is 1.1 to 1.4, which is 2-3. It was also found that the discharge capacity per unit volume of the negative electrode active material of the present invention was about 2 to 3 times larger than that of the calcined carbonaceous material.

Example 5 Example 1, No. 5 The same coin battery as in 1 was prepared and the following safety test was performed. 50mA coin battery 50mA /
After repeating 20 cycles of charging / discharging under the condition of cm ² , the battery was disassembled, the negative electrode pellet was taken out in 60% RH air, and a test as to whether or not spontaneous ignition was carried out.

Comparative Example 2 Instead of the negative electrode active material precursor, a Li-Al alloy (80%
-20% weight ratio, 15 mmΦ, 100 mg)
The same experiment as in Example 6 was performed.

As a result of Example 5 and Comparative Example 2, in the case of the compound of the present invention, no ignition was observed in all the batteries, whereas in Comparative Example 2, 32 negative electrode pellets were ignited. From this, it was shown that the compound of the present invention is a very safe compound.

[0098]

INDUSTRIAL APPLICABILITY As in the present invention, at least one of the negative electrode active materials is an oxide that inserts and releases lithium, and the non-aqueous electrolyte is 5% by volume or more and less than 30% by volume of ethylene carbonate and diethyl carbonate. By using a non-aqueous electrolyte in which a lithium salt containing fluorine is dissolved in a mixed solvent containing and, it is possible to obtain a safe non-aqueous secondary battery giving a high discharge operating voltage, a large discharge capacity and good charge-discharge cycle characteristics. You can

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a coin battery used in an example.

FIG. 2 is a cross-sectional view of a cylindrical battery used in an example.

[Explanation of symbols]

 1 Negative Electrode Sealing Plate 2 Negative Electrode Mixture Pellets 3 Separator 4 Positive Electrode Mixture Pellets 5 Current Collector 6 Positive Electrode Case 7 Gasket 8 Positive Electrode Sheet 9 Negative Electrode Sheet 10 Separator 11 Battery Can 12 Battery Lid 13 Gasket 14 Safety Valve

Claims (9)

[Claims] 1. A non-aqueous secondary battery comprising a positive electrode active material, a negative electrode active material, and a non-aqueous electrolyte, wherein at least one of the negative electrode active materials is an oxide that inserts and releases lithium, and the non-aqueous electrolyte is A non-aqueous secondary battery, which is a non-aqueous electrolyte in which a lithium salt containing fluorine is dissolved in a mixed solvent of 5% by volume or more and less than 30% by volume of ethylene carbonate and diethyl carbonate. 2. The non-aqueous electrolyte is 5% by volume or more and 30% by volume.
It is a non-aqueous electrolyte in which a lithium salt containing fluorine is dissolved in a mixed solvent of ethylene carbonate, diethyl carbonate, and at least one type of chain carbonate other than diethyl carbonate of less than 1. Non-aqueous secondary battery described 3. The non-water according to claim 2, wherein the chain carbonic acid ester is at least one selected from dimethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, methyl propyl carbonate and ethyl propyl carbonate. Secondary battery 4. The lithium salt of the organic electrolyte is LiXF.
n (X: B, P, As, Sb, n is 4 when X is B, X
The non-aqueous secondary battery according to any one of claims 1 to 3, further comprising a lithium salt represented by 6) when is P, As or Sb. 5. The non-aqueous secondary battery according to claim 4, wherein the lithium salt contains LiPF _6. 6. The lithium salt is LiPF.₆And LiBF
_Four, LiCF₃SO ₃At least one type selected from
6. A mixture with a thium salt, characterized in that
Non-aqueous secondary battery 7. The non-aqueous electrolyte according to claim 1, wherein the negative electrode active material is an oxide containing a metal group IVB or VB of the periodic table that inserts or releases lithium. Next battery 8. At least one of the negative electrode active materials is a transition metal oxide in which the basic crystal structure is changed by inserting lithium ions, and the basic crystal structure after the change is charged and discharged. 7. The non-aqueous secondary battery according to claim 1, wherein the non-aqueous secondary battery is at least one kind of lithium-containing transition metal oxide in a state that does not change. 9. The non-aqueous secondary battery according to claim 1, wherein the positive electrode active material is a lithium-containing transition metal oxide.