JPH0714610A - Nonaqueous secondary battery - Google Patents

Abstract

PURPOSE:To provide high discharge voltage and capacity by using a transition metal oxide as a negative active material, and a nonaqueous electrolyte prepared by dissolving a fluorine-containing lithium salt in a mixed solvent of ethylene carbonate and at least one chain ester. CONSTITUTION:A positive active material is a material capable reversibly of absorbing/desorbing lithium ions, preferably a lithium-containing transition metal compound. A negative active material is not limited to a transition metal oxide, but WO2 with rutile structure, a spinel compound such as LixFe(Fe2)O4, or lithium compound composed of Fe2O3 or the like is used. An organic electrolyte prepared by dissolving a fluorine-containing lithium salt in a mixed solvent containing ethylene carbonate and at lest one chain ester is used. Pyridine, triethyl phosphite, or triethanol amine may be added to the electrolyte to increase battery performance.

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 Lithium metal or a lithium alloy is typical as a negative electrode active material for a non-aqueous secondary battery. When it is used, lithium metal grows in a dendritic form during charge / discharge, which may cause an internal short circuit. , The activity of the dendritic metal itself is high, and there is a risk of ignition. On the other hand, recently, a calcined carbonaceous material capable of inserting and extracting lithium has come into practical use. This carbonaceous material is excellent in that the risk of ignition is relatively low and the charge / discharge capacity is high. However, the drawback is that lithium metal is deposited on the carbonaceous material during overcharging or rapid charging because it has conductivity, and eventually,
There is a problem that dendritic metal is deposited. In order to avoid this, we have devised a charger or adopted a method of reducing the amount of positive electrode active material to prevent overcharge, but the latter method limits the amount of active material. Therefore, the discharge capacity is also limited. Further, since the carbonaceous material has a relatively low density, the discharge capacity is limited in the dual sense that the capacity per volume is low.

Also used in these non-aqueous secondary batteries.
As a solvent for the electrolyte, propylene carbonate (P
C), ethylene carbonate (EC), butylene carbo
Cyclic carbonate such as nate (BC), γ-butyrolac
Tons (γ-BL), γ-valerolactone (γ-VL), etc.
Cyclic ester of dimethyl carbonate (DMC), diester
Chain carbonic acid ester such as ethyl carbonate (DEC),
Chain ester such as methyl acetate (MA), tetrahydro
Cyclic acids such as orchid (THF) and dioxolane (DOL)
Tellurium, dimethoxyethane (DME), diethyl ether
Use of non-aqueous solvent such as chain ether such as (DEE)
However, storage characteristics, cycle characteristics, and discharge characteristics have been investigated.
It has not been possible to obtain satisfactory battery performance such as battery performance.
Further, as the lithium salt of the electrolyte, LiClO_Four,
LiBF_Four, LiAsF₆, LiPF ₆, LiCF₃S
O₃What melt | dissolved the inorganic salt of these etc. is examined. Li
ClO_FourElectrolytes with high electric conductivity have high electrical conductivity
Under severe conditions, there is a drawback such as an explosion in the worst case.
Therefore, it is difficult to maintain safety. one
LiCF₃SO₃Is highly stable, and LiBF_Four, L
iAsF₆, LiPF₆Lewis acid double salts such as
These studies are mainly conducted because they are good. Only
However, a non-aqueous secondary battery using such a lithium salt
Battery with storage characteristics, cycle characteristics, discharge characteristics, etc.
There is no product that fully satisfies the performance.

On the other hand, as negative electrode active materials other than lithium metal, lithium alloys and carbonaceous materials, TiS ₂ and LiTiS ₂ capable of inserting and extracting lithium ions.
(US Pat. No. 3,983,476), WO with rutile structure
₂ (US Pat. No. 4,198,476), LixFe (F
e ₂ ) O ₄ and other spinel compounds (JP-A-58-22)
0,362), an electrochemically synthesized lithium compound of Fe2 O3 (US Pat. No. 4,464,447), Fe
Lithium compound of ₂ O ₃ (JP-A-3-112,07
0), Nb ₂ O ₅ (Japanese Patent Publication No. 62-59, 412, JP-A-2-824, 47), iron oxide, FeO, Fe ₂ O ₃ , F.
e ₃ O ₄ , cobalt oxide, CoO, Co ₂ O ₃ , Co ₃
O ₄ (JP-A-3-291,862) and the like are known.
Since all of these compounds have high redox potential,
It has not been possible to obtain a non-aqueous secondary battery having characteristics such as a V-class high discharge potential and high discharge capacity. As a combination of the positive electrode active material and the negative electrode active material, both of which are metal chalcogenides, TiS ₂ and LiTiS ₂ (US Pat.
476), chemically synthesized Li _0.1 V ₂ O ₅ and Li
Mn _1-s Mes O ₂ (0.1 <s <1 Me = transition metal; JP-A-63-210,028), chemically synthesized Li _0.1 V ₂ O ₅ and LiCo _1-s Fes O ₂ (S =
0.05-0.3; JP-A-63-211,564), chemically synthesized Li _0.1 V ₂ O ₅ and LiCo _1-s Ni
s O ₂ (s = 0.5 to 0.9; JP-A-1-294,36
4), V ₂ O ₅ and Nb ₂ O ₅ + lithium metal (JP-A-2
-82447), Lix Fe ₂ O ₃ electrochemically synthesized with V ₂ O ₅ and TiS ₂ (US Pat. No. 4,464,4).
47 Journal of Power Sources Volume 8 2
89, 1982), Li as a positive electrode active material and a negative electrode active material
_{NixCo1-x O 2 (0 ≦} x <1; JP-A 1-120,
765 In the specification, the positive electrode active material and the negative electrode active material are described as the same compound from Examples. ), LiCoO ₂
Or LiMn ₂ O ₄ and iron oxide, FeO, Fe
₂ O ₃ , Fe ₃ O ₄ , cobalt oxide, CoO, Co ₂ O
₃ or Co ₃ O ₄ (JP-A-3-291,862) is known. However, the discharge potential of the non-aqueous secondary battery of any combination of these is lower than 3 V, and the discharge capacity cannot be said to be sufficiently high. However, in recent years, a transition metal oxide in which the basic structure of the crystal is changed by inserting lithium ions, the negative electrode active material in a state in which the basic structure of the crystal after the change is not changed by charge and discharge is proposed, A non-aqueous secondary battery having high discharge potential, high discharge capacity (high energy density), long charge / discharge cycle life, and high safety was obtained. (Japanese Patent Application No. 5-120908) However, even with this improved non-aqueous secondary battery, the battery performance at low temperature is not satisfactory, and further improvement is required.

[0005]

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.

[0006]

The present invention relates to a non-aqueous secondary battery comprising a positive electrode active material, a negative electrode active material and an organic electrolyte,
Transition metal oxide as the negative electrode active material, as the organic electrolyte,
The non-aqueous secondary battery is characterized by using a non-aqueous electrolyte in which a lithium salt containing fluorine is dissolved in a mixed solvent containing ethylene carbonate and at least one chain ester.

The transition metal in the present invention has an element number of 21.
From Sc of element No. 30 to Zn of the element number 39 to Y of the element number 39 to Cd of the element number 48 and La of the element number 57 to Hg of the element number 80.

The mixed solvent used in the electrolyte of the present invention is
It is a mixed solvent containing ethylene carbonate and at least one chain ester, or ethylene carbonate, at least one chain ester and at least one chain carbonate. The mixed solvent may further include any organic solvent. The chain ester is preferably methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, isopropyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, methyl malonate, ethyl malonate, methyl succinate, ethyl succinate. , Methyl 3-methoxypropionate and ethyl 3-methoxypropionate, and more preferably methyl propionate, ethyl propionate, methyl 3-methoxypropionate and ethyl 3-methoxypropionate. The chain carbonic acid ester is preferably at least one selected from diethyl carbonate, dimethyl carbonate and methyl ethyl carbonate, and more preferably diethyl carbonate. A particularly preferred mixed solvent used in the electrolyte of the present invention is a mixed solvent containing ethylene carbonate, dimethyl carbonate and / or diethyl carbonate, and methyl propionate and / or ethyl propionate. Most preferably, it is a mixed solvent containing ethylene carbonate, diethyl carbonate, methyl propionate and / or ethyl propionate.

In the present invention, the amount of each solvent in the mixed solvent is not particularly limited, but ethylene carbonate is preferably 5% by volume or more and less than 40% by volume of the mixed solvent, particularly preferably 5% by volume or more and 30% by volume. Is less than. Most preferably, it is 10% by volume or more and less than 30% by volume. The chain ester and chain carbonate ester to be mixed with ethylene carbonate are preferably 5 to 70% by volume, particularly preferably 10 to 70% by volume. Most preferably 10-60
% By volume.

The lithium salt used in the electrolyte of the present invention is a lithium salt containing fluorine, and a specific example is LiB.
_{F 4, LiPF 6, LiAsF 6} , LiSbF 6, LiCF
₃ SO ₃ , LiCF ₃ CO _{2 and the} like can be mentioned, but the compounds are not particularly limited to these. Preferred lithium salts are LiCF ₃ SO ₃ , LiXFn (X: B,
P, As, Sb, n is 4 when X is B, and X is P, As,
When Sb is 6). LiXFn is a Lewis acid double salt represented by LiF + XFn- _1- > LiXFn, and specific examples include LiBF
_{4, LiPF 6, LiAsF 6,} LiSbF 6 , and the like. More preferably, LiBF ₄ , LiPF ₆ , LiCF
₃ SO ₃ , particularly preferably LiPF ₆ , LiCF ₃
SO ₃ and most preferably LiPF ₆ .

In the present invention, the lithium salt concentration of 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.

Besides 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, and Cr.
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.

The lithium-containing transition metal oxide which is the positive electrode active material of the present invention comprises a lithium compound and one or more transition metal compounds, and the molar ratio of lithium compound / total transition metal compound is 0.3 to 2. It is preferable to mix and synthesize so as to be 0.2. (However, the transition metal is Ti,
At least one selected from V, Cr, Mn, Fe, Co, Ni, Mo and W). Furthermore, as the transition metal,
It is preferably at least one selected from V, Cr, Mn, Fe, Co and Ni.

The lithium-containing transition metal oxide, which is the positive electrode active material of the present invention, is Liy MOz (where M is Co,
A transition metal containing at least one selected from Mn, Ni, V and Fe, y is in the range of 0.3 to 1.2, and z is in the range of 1.4 to 3).

Preferred Lithium-Containing Metal Oxides of the Invention
As a positive electrode active material of Liy CoO₂, Liy NiO
₂, Liy Co_aNi_1-aO₂, Liy Cob V_1-bO
z, Liy Cob Fe_1-bO₂, Liy Mn₂O_Four, L
iy Mnc Co_2-cO_Four, Liy Mnc Ni_2-cO_Four,
Liy Mnc V_2-cO_FourAnd Liy Mnc Fe
_2-cO _Four, And Liy Mn₂O_FourAnd MnO₂Mixed with
Thing, Li₂yMn₂O₃And MnO ₂A mixture with, and Li
y Mn₂O_Four, Li₂yMn₂O₃And MnO₂Mixture with
(However, y is in the range of 0.5 to 1.2, and a is 0.1.
Is in the range of 0.9 and b is in the range of 0.8 to 0.98.
, C is in the range 1.6 to 1.96, and z is
2.01 to 5).

More preferred lithium-containing metal oxide positive electrode active materials of the present invention include LiyCoO ₂ and Liy N
iO ₂ , Liy Co _a Ni _1-a O ₂ , Liy Cob V
_1-b Oz, Liy Cob Fe _1-b O ₂ , Liy Mn ₂ O
₄ , Liy Mnc Co _2-c O ₄ , Liy Mnc Ni _2-c
O ₄ , Liy Mnc V _2-c O ₄ , Liy Mnc Fe _2-c
O ₄ (however, y is in the range of 0.7 to 1.04, a is in the range of 0.1 to 0.9, b is in the range of 0.8 to 0.98, and c is 1 .6 to 1.96 and z is in the range 2.01 to 2.3).

The most preferable lithium-containing transition metal oxides of the present invention are Liy CoO ₂ and Liy NiO.
₂ , Liy Coa Ni _1-a O ₂ , Liy Mn ₂ O ₄ , L
iyCob V _1-b Oz (where y is in the range of 0.7 to 1.1, a is in the range of 0.1 to 0.9, and b is 0.
9 to 0.98 and z is 2.01-2.
3). Furthermore, y is in the range 0.7 to 1.04, a is in the range 0.1 to 0.9, b is in the range 0.9 to 0.98, and z is 2.02. It is preferably in the range of to 2.3.

Here, the above-mentioned y value is a value before the start of charging / discharging and increases / decreases due to charging / discharging. The positive electrode active material used in the present invention may be crystalline or amorphous, but a crystalline compound is preferable.

The transition metal oxide of the negative electrode active material used in the present invention is not particularly limited, and specific examples thereof include WO _{2 having} a rutile structure (US Pat. No. 4,198,476) and Li.
Spinel compounds such as xFe (Fe ₂ ) O ₄
8-220, 362), electrochemically synthesized Fe ₂
Lithium compounds of O ₃ (US Pat. No. 4,464,44
7), a lithium compound of Fe ₂ O ₃ (Japanese Patent Laid-Open No. 3-11
2,070), Nb ₂ O ₅ (Japanese Patent Publication No. 62-59, 41)
2, JP-A-2-82,447), iron oxide, FeO, Fe
₂ O ₃ , Fe ₃ O ₄ , cobalt oxide, CoO, Co ₂ O
₃ , Co ₃ O ₄ (JP-A-3-291,862). Preferable are transition metal oxides 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 where it does not change due to charge and discharge. (Japanese Patent Application No. 5-120
908)

A preferred transition metal oxide of the present invention, in which the basic structure of the crystal is changed by inserting lithium ions, wherein the basic structure of the crystal after the change is in a state where it does not change due to 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 before insertion of lithium ions used in the present invention (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 that is the negative electrode active material precursor of the present invention is Lip
MOj (where M represents at least one transition metal and at least one of the transition metals is Ti, V, M
n, Co, Ni, Fe, 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). The above negative electrode active material precursor is further subjected to Lip M ₂ q ₁ M
₂ q ₂ ··· Mnqn Oj (where each of M ₁ M ₂ ··· 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, and 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 in the range 0.2-3.1, n is in the range 1-4, and j is 1.8-.
It is more preferably in the range of 4.1. Particularly, in the above formula, p is in the range of 0.2 to 3.1 and n is 1 to
Preferably, it is in the range 3 and j is in the range 1.8 to 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

Examples of the negative electrode active material precursor containing V include:
Lip M ₁ q ₁ M ₂ q ₂ ... Mnqn VqvOj (where M is a transition metal and p is in the range of 0 to 3.1, q ₁
+ Q2 + ... + qn + qv = 1, n is in the range 1-9, and j is in the range 1.3-4.1)
Is preferred. Further, the negative electrode active material precursor containing V is Lip M ₁ q ₁ M ₂ q ₂ V 1- (q ₁ + q ₂ ) Oj (provided that M
Is a transition metal, p is in the range of 0.2 to 3.1,
q ₁ + q ₂ is in the range 0-0.7, and j is 1.
It is more preferably in the range of 3 to 4.1). The negative electrode active material precursor containing V is Lip C
oq V _1-q Oj, Lip Niq V _1-q Oj (where p is in the range of 0.3 to 2.2, q is in the range of 0.02 to 0.7, and j is 1. 5 to 2.5)
Is most preferable.

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, Lip M
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 following compounds are listed as examples of the negative electrode active material precursor of the present invention, but the present invention is not limited to these compounds. For example, LiVO _3.1 , LiTiO _2.3 , CoVO
_{3. 7, LiCoVO 4.0, LiCo} 0.5 V 0.5 O 2.1, Li
_{NiVO 4.0, Li 0.75 Ni 0 .5} V 0.5 O 2.1, Li 1.75
Ni _0.5 V _0.5 O _2.4 , LiTi _0.5 V _0.5 O _2.9 , LiMn
_0.5 V _0.5 O _2.5 , LiFe _0.5 Mn _0.5 O _2.1 , LiCo
_0.25 V _0.75 O _2.8 , LiNi _0.25 V _0.75 O _2.7 , LiNi
_0.05 V _0.95 O _3.1 , LiFe _0.05 V _0.95 O _3.1 , LiMn
_0.05 V _0.95 O _3.0 , LiCa _0.05 V _0.95 O _3.2 , LiCo
_{0.75 V 0.25 O 1. 9, LiMn} 0.25 Ti 0.5 V 0.25 O 2.6,
LiCr _0.05 V _0.95 O _3.2 , LiNb _0.05 V _0.95 O _3.1 ,
LiMo _0.05 V _0.95 O _3.0 . The oxygen number is a value obtained from the weight of the compound before firing and the weight after firing.
Therefore, the oxygen number is -10 to the above value due to the accuracy of the measuring method.
It is necessary to add an error of 10%.

The preferred negative electrode active material of the present invention is one in which lithium ions are inserted 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 preferable negative electrode active material precursor is Lix MOj (where M represents at least one transition metal and transition metal). At least one of Ti, V, Mn, Co, Fe, Ni, Nb, and Mo is selected, 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 insertion amount of lithium ions is not particularly limited, but the negative electrode active material precursor 1
27 to 1340 mAh (corresponding to 1 to 50 mmol) per g is preferable. In particular, 40 to 1070 mAh (1.5 to 40
(equivalent to mmol) is preferred. And 54 to 938 mAh
(Corresponding to 2 to 35 mmol) is most preferable. The use ratio of the positive electrode active material and the negative electrode active material is not particularly limited, but it is preferable to set them so that the effective equivalents are equal to each other (the effective equivalent is an equivalent that can substantially maintain the cycle property). ). At that time, it is also preferable to increase the amount of either the positive electrode active material or the negative electrode active material. 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 voltage that can increase the discharge voltage and substantially maintain the cycleability. Is preferred.

The negative electrode active material thus obtained is one in which the basic structure of the crystal of this precursor has been changed, and this change is preferably from the diffraction angle (2θ) 5 of the X-ray diffraction pattern by CuKα rays. 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. Further, as a standard compound, the signal intensity of the main peak of LiCoO ₂ 2θ = 18.9 ° (4.691Å) was 7990 cps. (Synthesis method of LiCoO ₂ : Li ₂ CO ₃ and CoCO ₃ were mixed in a mortar so that Li / Co = 1 (molar ratio) and transferred to a magnetic crucible,
After left at 130 ° C. for 1 hour, it is 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.

Further, 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 and contracts due to the absorption and desorption of lithium ions. It means that the bond distance 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) interval obtained from the peak value of the X-ray diffraction method is preferably −0.1 to 0.1Å, and further −0.
05-0.05Å is preferable. 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, the negative electrode active material precursor LiCoVO ₄ is V ₅₊ (Li + C
The inverse spinel structure expressed by o ₂₊ ) O ₄ changes the crystal structure when lithium ions are electrochemically inserted into this oxide, and an unknown crystal structure that gives a broad peak around 2 Å or Change to an amorphous structure. 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 composition formulas of the positive electrode active material and the negative electrode active material are different" means 1. Different combinations of metal elements, and 2. Positive active material Liy Cob V _1-b O
In the example of z and the negative electrode active material Lix Coq V _1-q Oj, it 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 positive electrode active material of the present invention comprises a method of chemically inserting lithium ions into a transition metal oxide, a method of electrochemically inserting lithium ions into a transition metal oxide, a method of mixing a lithium compound and a transition metal compound, It can be synthesized by firing.

In synthesizing the positive electrode active material of the present invention, a method of inserting lithium ions into the transition metal oxide is preferably a method of synthesizing lithium metal, a lithium alloy or butyllithium with the transition metal oxide. . The positive electrode active material used in the present invention is particularly preferably synthesized by mixing a lithium compound and a transition metal compound and firing.

The negative electrode active material precursor of the present invention can also be synthesized by a method of mixing and firing a lithium compound and a transition metal compound or a solution reaction, but the firing method is particularly preferable. The firing temperature used in the present invention may be a temperature at which a part of the mixed compound used in the present invention is decomposed and melted, and for example, 250 to 2000 ° C is preferable,
Particularly, 350 to 1500 ° C. is preferable. 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,
It is preferable that the negative electrode active material is 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). 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 generated. As described above, a compound having a low activity as a negative electrode active material precursor may be included in the synthesis process. Although such compounds may be included,
It may be removed if desired.

The negative electrode active material precursor and the positive 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,
The same transition metal complex salt is used.

Preferred lithium compounds which 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 transition metal compounds which can be used in the present invention are TiO 2, titanyl ammonium oxalate, VOd (d = 2 to 2.5), lithium compounds of VOd, ammonium metavanadate, MnO ₂ ,
Mn ₂ O ₃ , manganese hydroxide, manganese carbonate, manganese nitrate, manganese ammonium sulfate, manganese acetate, manganese oxalate, manganese citrate, iron oxide (2,3 valent), ferric oxide, iron hydroxide (2,3) Value), iron acetate (2, 3
Valence), iron citrate (2,3 valence), ammonium iron citrate (2,3 valence), iron oxalate (2,3 valence), ammonium iron oxalate (2,3 valence), 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, copper oxide (1, Divalent), copper hydroxide, copper acetate, copper citrate, M
oO ₃ , MoO ₂ , LiMo ₂ O ₄ , WO ₂ and WO ₃ 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₊ ,
(For example, calcium carbonate, calcium chloride, calcium oxide, calcium hydroxide, calcium sulfate, calcium nitrate, calcium acetate, calcium oxalate, calcium citrate, calcium phosphate) or amorphous formation containing P, B, Si Agents (eg P ₂ O ₅ , Li ₃ P
O ₄ , H ₃ BO ₃ , SiO _{2 and the} like) may be mixed and fired. In addition, alkali metal ions such as Na, K and Mg and / or Sn, Al, Ga, Ge, Ce and I
You may mix with a compound containing n, 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.

The average particle size of the positive electrode active material and the negative electrode active material used in the present invention is not particularly limited, but is 0.03 to
50 μm is preferable. A known crusher or classifier can be used to obtain a predetermined particle size. For example,
Mortar, ball mill, vibrating ball mill, satellite ball mill,
A swirling airflow type jet mill, a sieve, etc. can be mentioned.

The chemical formula of the compound obtained by firing was calculated by an inductively coupled plasma (ICP) emission spectroscopy as a measuring method, and as a simple method from the weight difference between the powders before and after firing.

The positive electrode active material and the negative electrode active material used in the present invention obtained as described above are both considered to be compounds that occlude and release lithium ions and change the valence of the transition metal upon charge and discharge. 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. Similarly, carbon is not a compound whose valency is clearly changed as compared with a carbonaceous compound, and is a compound which has high conductivity and 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.

Materials that can be used with the negative electrode active material of the present invention include lithium metal and lithium alloys (Al, Al-
Mn (US Pat. No. 4,820,599), Al-Mg
(JP-A-57-98977), Al-Sn (JP-A-63-6742), Al-In, Al-Cd.
(JP-A-1-144573) or the like, or a calcined carbonaceous compound capable of occluding and releasing lithium ions or lithium metal (for example, JP-A-58-209864, JP-A-61-214417, JP-A-62-162). 88269, JP-A-62-216170, JP-A-63-
13282, JP 63-24555, JP 63-12147, and JP 63-1212.
57, JP-A-63-155568, JP-A-63-276873, and JP-A-63-314821.
JP, JP-A-1-204361, JP, 1-2
21859, JP-A-1-274360 and the like). The purpose of the combined use of the lithium metal or lithium alloy is to insert lithium ions into the battery, and does not utilize the dissolution and precipitation reaction of lithium metal or the like as the battery reaction.

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
No. 48554), 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 1
-50% by weight is preferable, and 2-30% by weight is particularly preferable. For carbon and graphite, 2 to 15% by weight is particularly preferable.

As the binder, one kind of polysaccharides, thermoplastic resins and polymers having rubber elasticity or a mixture thereof can be used. Preferred examples are starch, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose,
Diacetyl cellulose, polyvinyl chloride, polyvinylpyrrolidone, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber, polybutadiene, fluororubber and polyethylene oxide. Can be mentioned. 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 2
-30% by weight is preferred. 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.

Other compounds may be added to the electrolyte for the purpose of improving discharge and charge / discharge characteristics. For example, pyridine (JP-A-49-108525), triethylphosphite (JP-A-47-4376), triethanolamine (JP-A-52-72425), cyclic ether (JP-A-57-57425). 152684), ethylenediamine (JP-A-58-87777), n-glyme (JP-A-58-87778), hexaphosphoric acid triamide (JP-A-58-8777).
9), nitrobenzene derivatives (JP-A-58-21)
No. 4281), sulfur (JP-A-59-8280), quinoneimine dye (JP-A-59-68184), N-substituted oxazolidinone and N, N'-substituted imidazolidinone (JP-A-59-154778). Gazette), ethylene glycol dialkyl ether (JP-A-59-20)
No. 5167), quaternary ammonium salts (Japanese Patent Laid-Open No. Sho 60).
-30065), polyethylene glycol (JP-A-60-41773), pyrrole (JP-A-60-).
79677), 2-methoxyethanol (JP-A-60-
89075), AlCl3 (JP-A-61-884).
No. 66), a monomer of a conductive polymer electrode active material (JP-A-61-161673), triethylenephosphoramide (JP-A-61-208758), trialkylphosphine (JP-A-62-80976). No.), morpholine (JP-A-62-80977),
Aryl compounds having a carbonyl group (JP-A-62-86)
No. 673), crown ethers such as 12-crown 4 (Physical Review)
B, 42, 6424 (1990)), hexamethylphosphoric triamide and 4-alkylmorpholine (JP-A-62-217575), and bicyclic tertiary amine (JP-A-62-217578). Gazette), oil (JP-A-62-287580), quaternary phosphonium salt (JP-A-63-1212268), tertiary sulfonium salt (JP-A-63-1212269), 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-48-36,6).
32). Further, the electrolytic solution may contain carbon dioxide gas in order to have suitability for high temperature storage (JP-A-59-13).
4567). Further, the mixture of the positive electrode and the negative electrode can contain an electrolytic solution or an electrolyte. For example, the ion-conductive polymer or nitromethane (Japanese Patent Laid-Open No. 48-3
6633), electrolytic solution (JP-A-57-124870).
(Japanese Patent Publication) is known.

The surface of the positive electrode active material can be modified. For example, the surface of a metal oxide is treated with an esterifying agent (JP-A-55-163779) or a chelating agent (JP-A-55-163780), a conductive polymer (special Examples of the treatment include treatments with JP-A-58-163188, JP-A-59-14274), polyethylene oxide and the like (JP-A-60-97561). 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-58-142771).
Processing).

The collector of the electrode active material may be any electron conductor that 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 method of mixing powders of an active material, a conductive agent, a binder and the like in a dry method or a method of adding water or an organic solvent and wet mixing is preferable. 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, iron, nickel, titanium, chromium,
Metals such as molybdenum, copper and aluminum or alloys thereof are used. As a method for welding the cap, the can, 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 application of the non-aqueous secondary battery of the present invention is not particularly limited, and specific examples include color notebook computers, black and white notebook computers, pen input computers, pocket (palm top) computers, notebook word processors, pocket word processors, and electronic devices. 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, electric shaver, electronic translator, mobile phone, Specific low power transceiver, power tool, electronic notebook,
Calculator, memory card, electronic tape recorder, clock,
Examples include cameras and hearing aids.

[0061]

EXAMPLES The present invention will be described in more detail with reference to specific examples below, but the present invention is not limited to the examples as long as the gist of the invention is not exceeded. Example 1 A mixture of 82% by weight of LiCoO ₂ (a) as a positive electrode active material, 12% by weight of flake graphite as a conductive agent, and 6% by weight of polytetrafluoroethylene as a binder was compressed. Molded positive electrode pellets (13 mmΦ, 0.
35 g) was thoroughly dehydrated with a far infrared heater in a dry box (dew point −40 to −70 ° C., dry air) and used as a positive electrode material. LiCoVO as a negative electrode active material precursor
₄ (A) (lithium carbonate, cobalt oxide and vanadium pentoxide in air at 750 ° C. for 12 hours) 82% by weight, scaly graphite 12% by weight as a conductive agent, and polyvinylidene fluoride as a binder. Was mixed at a mixing ratio of 6% by weight, and a negative electrode pellet (13 mmΦ, 0.
060 g) was thoroughly dehydrated with a far infrared heater in the same dry box as above and used as a negative electrode material. As the current collector, a SUS316 net having a thickness of 80 μm was welded to a coin can for both the positive and negative electrode cans. 2 electrolytes shown in Table 1
50 μl was used, and further, a microporous polypropylene sheet and a polypropylene non-woven fabric were used as a separator, and the non-woven fabric was impregnated with the electrolyte. Then, a coin type lithium battery as shown in FIG. 1 was produced in the same dry box as above.

[0062]

[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 and negative electrode mixture pellets 4 are enclosed between the positive electrode case 6 having the above and the separator 3, and a 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. Keeping this lithium battery at 22 ° C.,
3.9 to 1.8 V at a constant current density of 75 mA / cm ^2.
The charge / discharge test was performed in the range of. (Charging was performed up to 3.9 V, and discharging was performed up to 1.8 V (1 cycle). All the tests were started from charging.) Also, -10
A test similar to that at 22 ° C was performed at 0 ° C.

The evaluation results are shown in Table 2. The abbreviations shown in Table 2 (the same applies to Table 3) are as follows. (A) Second cycle discharge capacity (negative electrode active material 1 g
Per mAh), (a) average discharge voltage (V) in the second cycle, (c) number of cycles (number of cycles until the capacity reaches 60% of the maximum capacity), and above (a) (b) (c) Is 2
Performed at 2 ° C. (D) Discharge capacity at the second cycle at −10 ° C. (mAh per 1 g of the negative electrode active material).

[0065]

[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 _2.0 (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 LiCoVO ₄ (A), L
_{i 1.0 Co 0.5 V 0.5 O 2.} 0 (B) (90 lithium carbonate and cobalt ammonium metavanadate carbonate in air
A battery was prepared in the same manner as in Example 1 except that 0 ° C. was fired for 6 hours) or rutile type WO ₂ (C) was used. The results are shown in Table 3.

[0068]

[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. Propylene carbonate + dimethoxyethane (volume ratio 1: 1) 1M LiBF ₄ 17. Ethylene carbonate + acetonitrile (volume ratio 1: 1) 1M LiBF ₄ 18. Ethylene carbonate + dimethylformamide (volume ratio 1: 1) 1M LiBF ₄ 19. Propylene carbonate + dimethyl carbonate +
Dimethoxyethane (volume ratio 1: 1: 1) 1M LiBF
_Four

The results of Examples 1 to 3 and Comparative Example 1 showed that the compounds of the present invention had a high discharge voltage, a long charge / discharge cycle and a large discharge capacity. 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 4 In Example 1, No. The same coin battery as in 2 was prepared and the following safety test was carried out. 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 3 Instead of the negative electrode active material precursor, a Li-Al alloy (80%
The same experiment as in Example 4 was performed using a -20% weight ratio, 15 mmΦ, 1.0 g).

As a result of Example 4 and Comparative Example 3, in the compound of the present invention, no ignition was observed in all the batteries, whereas in Comparative Example-3, 30 negative electrode pellets were ignited. From this, it was shown that the compound of the present invention is a very safe compound.

[0074]

As in the present invention, a mixed solvent containing a transition metal oxide as a negative electrode active material, ethylene carbonate as an organic electrolyte, and at least one chain ester,
By using a non-aqueous electrolyte in which a lithium salt containing fluorine is dissolved, it is possible to obtain a safe non-aqueous secondary battery that provides a high discharge operating voltage, a large discharge capacity and good charge / discharge cycle characteristics.

[Brief description of drawings]

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

[Explanation of symbols]

 1 Negative Electrode Sealing Plate 2 Negative Electrode Mixture Pellet 3 Separator 4 Positive Electrode Mixture Pellet 5 Current Collector 6 Positive Electrode Case 7 Gasket

Claims (7)

[Claims] 1. A non-aqueous secondary battery comprising a positive electrode active material, a negative electrode active material, and an organic electrolyte, wherein a transition metal oxide is used as the negative electrode active material, and ethylene carbonate is used as the organic electrolyte.
A non-aqueous secondary battery characterized by using a non-aqueous electrolyte in which a lithium salt containing fluorine is dissolved in a mixed solvent containing at least one kind of chain ester. 2. The negative electrode active material 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 does not change due to charge and discharge. The non-aqueous secondary battery according to claim 1, wherein the non-aqueous secondary battery is at least one transition metal oxide containing lithium. 3. A non-aqueous electrolyte prepared by dissolving a lithium salt containing fluorine in a mixed solvent containing ethylene carbonate, at least one chain ester and at least one chain carbonate as the organic electrolyte. The non-aqueous secondary battery according to claim 1 or 2, characterized in that 4. The chain ester is at least one selected from methyl propionate, ethyl propionate, methyl 3-methoxypropionate, and 3-methoxyxypropionethyl. Item 3. The non-aqueous secondary battery according to item 3. 5. The non-aqueous secondary battery according to claim 1, wherein the chain carbonic acid ester is at least one selected from diethyl carbonate, dimethyl carbonate, and methyl ethyl carbonate. 6. The lithium salt of the organic electrolyte is LiXF.
n (X: B, P, As, Sb, n is 4 when X is B, X
Is P, As, Sb, 6) and LiCF ₃ SO _{3 is} selected from the non-aqueous secondary batteries according to claim 1. 7. The lithium salt of the organic electrolyte is LiPF.
Non-aqueous secondary battery according to claim 6, wherein it is ₆