JPH10116631A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery having high capacity and an excellent charge and discharge cycle characteristic. SOLUTION: In a nonaqueous electrolyte secondary battery comprising a positive electrode 5 and a negative electrode 4 containing material capable of reversibly storing and discharging lithium, nonaqueous electrolyte 6 containing lithium salt, and a separator 3, the nonaqueous electrolyte 6 contains cyclic carbonate, chain carbonate, and cyclic ether of 0.1% by volume or more and 7% by volume or less, moisture content is 1ppm or more and 50ppm or less, and free acid portion as HF is 2ppm or more and 100ppm or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-capacity non-aqueous electrolyte secondary battery having excellent charge-discharge cycle characteristics, and more particularly, to a non-aqueous electrolyte using an electrolyte solution having excellent charge-discharge cycle characteristics and a negative electrode material having a large discharge capacity. The present invention relates to a water electrolyte secondary battery.

[0002]

2. Description of the Related Art It has been known that the composition of a non-aqueous electrolyte greatly affects the charge / discharge cycle stability of a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery. Japanese Patent No. 64240 proposes a method using lithium trifluoromethanesulfonate as a lithium salt in a mixed solvent consisting of a cyclic carbonate, a chain carbonate and an ether in a specific amount range.

In Japanese Patent Application Laid-Open No. Hei 8-130036, it is proposed to use a composite oxide of a metal having a high discharge capacity for a negative electrode and use a mixed solvent of ethylene carbonate and a chain carbonate for a non-aqueous electrolyte. I have.

[0004] Although these proposals show a certain improvement effect, they do not greatly improve the situation of reducing the discharge capacity inherent in the electrode material in order to secure the cycle stability.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a non-aqueous secondary battery which achieves both high discharge capacity and charge / discharge cycle stability, and has high capacity and excellent cycle stability.

[0006]

The present inventors have found that the specific solvent composition of the non-aqueous electrolyte, particularly the presence of cyclic ethers and the control of water content and free acid content, have a remarkable effect on solving the above problems. This has led to the present invention.

An object of the present invention is to provide a non-aqueous electrolyte secondary battery comprising a positive electrode and a negative electrode containing a material capable of reversibly inserting and extracting lithium, a non-aqueous electrolyte containing a lithium salt, and a separator. A non-cyclic carbonate comprising a cyclic carbonate, a chain carbonate and 0.1% to 7% by volume of a cyclic ether, a water content of 0.5 ppm to 50 ppm, and a free acid content of 2 ppm to 100 ppm as HF. The problem was solved by a water electrolyte secondary battery.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the following forms can be used, but the present invention is not limited to these.

(1) In a nonaqueous electrolyte secondary battery comprising a positive electrode and a negative electrode containing a material capable of reversibly inserting and extracting lithium, a nonaqueous electrolyte containing a lithium salt, and a separator, the nonaqueous electrolyte is a cyclic carbonate And a chain carbonate and 0.1% to 7% by volume of a cyclic ether, having a water content of 0.5 ppm to 50 ppm and a free acid content of HF
A non-aqueous electrolyte secondary battery characterized by being at least 2 ppm and at most 100 ppm.

(2) The non-aqueous electrolyte secondary battery according to item 1, wherein the lithium salt contained in the non-aqueous electrolyte contains LiPF ₆ and LiBF ₄ .

(3) The non-aqueous electrolyte secondary battery according to item 1 or 2, wherein the cyclic ether is represented by the following general formula (1).

[0012]

Embedded image In the formula, R ¹ and R ² may be the same or different and each represent a hydrogen atom or an alkyl group having 8 or less carbon atoms.

(4) The nonaqueous electrolyte secondary battery according to item 3, wherein R ¹ and R ² of the cyclic ether are a hydrogen atom or an alkyl group having 4 or less carbon atoms.

(5) The electrolyte is characterized in that the content of the cyclic carbonate is 5% by volume or more and 30% by volume or less, and the content of the chain carbonate is 60% by volume or more and 90% by volume or less. Item 5. The non-aqueous electrolyte secondary battery according to any one of Items 1 to 4.

(6) The electrolytic solution has a cyclic carbonate content of 15 vol% to 26 vol%, a chain carbonate content of 71 vol% to 85 vol%, and a cyclic ether content of Item 5. The non-aqueous electrolyte secondary battery according to any one of Items 1 to 4, wherein the content is 0.3% by volume or more and 5% by volume or less.

(7) The non-aqueous electrolyte secondary battery according to any one of items 1 to 6, wherein at least one kind of the negative electrode material is represented by the following general formula (2).

M ¹ M ² _p M ⁴ _q M ⁶ _r General formula (2) (where M ¹ and M ² are different from each other, Si, Ge, Sn, P
at least one selected from b, P, B, Al, and Sb;
M ⁴ is Li, Na, K, Rb, Cs, Mg, Ca, S
at least one selected from r and Ba, M ⁶ is O, S,
At least one selected from Te, p and q are each 0.0
01 to 10, r represents a number of 1.00 to 50. )

Hereinafter, the configuration of the nonaqueous secondary battery according to one embodiment of the present invention will be described in detail.

The non-aqueous electrolyte used in the non-aqueous secondary battery of the present invention contains 0.1% by volume of cyclic carbonate and chain carbonate.
Not less than 7% by volume and a water content of 0.5% or less.
ppm to 50 ppm and free acid content is 2 ppm to 1 as HF
It is characterized by being at most 00 ppm. The cyclic carbonates, chain carbonates and cyclic ethers of the electrolyte solvent have been conventionally known both when used alone and when used in combination. Also, it is generally known that reducing the water content and free acid content in the electrolyte improves the charge / discharge stability of the secondary battery. However,
Controlling the water content from 0.5 ppm to 50 ppm and the free acid content to 2 ppm to 100 ppm in terms of HF has a remarkable cycle stabilizing effect. It is a new finding that high capacity and cycle stability are compatible when using a negative electrode material.

The cyclic carbonate which can be used in the present invention includes, for example, ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-
Butylene carbonate, 1,2-pentene carbonate,
2,3-pentene carbonate can be mentioned. Of these, ethylene carbonate is particularly preferred.

The chain carbonate ester has 3 to 3 carbon atoms.
8 can be used. Among these, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate are preferred. Particularly preferred are dimethyl carbonate and diethyl carbonate. Dimethyl carbonate and diethyl carbonate may be used in combination.

Examples of the cyclic ether which can be used in the present invention include tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolan, 1,3-dioxane, 1,4-dioxane, trioxane and derivatives thereof. it can. More preferred are 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane and derivatives thereof, and most preferred are 1,3-dioxolane represented by the following general formula (1) and derivatives thereof. .

[0023]

Embedded image

In the formula, R ¹ and R ² may be the same or different and each represents a hydrogen atom or an alkyl group having 8 or less carbon atoms. More preferably, they are a hydrogen atom or an alkyl group having 4 or less carbon atoms, and particularly preferably a hydrogen atom, a methyl group or an ethyl group. For example, 1,3-dioxolan, 2-methyl-1,3-dioxolan, 2,2-dimethyl-1,3-dioxolan, 4-methyl-1,3-dioxolan, 2-ethyl-
1,3-dioxolane, 4-ethyl-1,3-dioxolane, 2
-Methyl-4-ethyl-1, 3-dioxolan, and the like.

The mixing ratio of each solvent in the non-aqueous electrolyte of the present invention is such that cyclic carbonate is 5 to 30% by volume, chain carbonate is 60 to 90% by volume, and cyclic ether is 0.1 to 7% by volume. Certain cases are preferred. More preferably, the cyclic carbonate is 10 to 28% by volume, and the chain carbonate is 67 to
The mixing ratio is 88% by volume and the cyclic ether is 0.2 to 6% by volume. Particularly preferably, the cyclic carbonate is 15 to 2
6% by volume, 71 to 85% by volume of chain carbonate, and 0.3 to 5% by volume of cyclic ether.

The non-aqueous electrolyte of the present invention further includes γ-butyrolactone, methyl formate, methyl acetate, 1,2-dimethoxyethane, dimethyl sulfoxide, formamide, dimethylformamide, acetonitrile, nitromethane, ethyl monoglyme, triphosphate Esters, trimethoxyethane, sulfolane, 3-methyl-2-oxazolidinone,
An aprotic organic solvent such as ethyl ether, 1,3-propane sultone can be added.

The supporting salt which can be used in the non-aqueous electrolyte of the present invention includes, for example, LiClO ₄ , LiBF ₄ , LiP
F ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ ,
LiSbF ₆ , LiB ₁₀ Cl ₁₀ , lithium lower aliphatic carboxylate, LiAlCl ₄ , LiCl, LiBr, Li
Li salts such as I, lithium chloroborane, lithium tetraphenylborate and the like can be mentioned, and one kind or a mixture of two or more kinds can be used. Above all, L
The use of iBF ₄ or LiPF ₆ is preferred. Furthermore, Li
It is preferable to use BF ₄ and LiPF ₆ in combination.

The concentration of the supporting salt is not particularly limited, but is preferably 0.2 to 3 mol per liter of the electrolytic solution. The amount of these electrolytes to be added to the battery is not particularly limited, but can be determined as appropriate depending on the amount of the electrode material and the size of the battery.

It is desirable that the amount of water contained in the electrolyte of the present invention is as small as possible. The water content is preferably 50 ppm or less, more preferably 40 ppm or less, and particularly preferably 30 ppm or less. It is desirable that the lower limit of water content is lower, but 0.5 ppm
It is difficult to control below. In order to reduce the water content, it is necessary to sufficiently dehydrate the organic solvent and the supporting electrolyte used when preparing the electrolyte and to keep the atmosphere during the preparation at a low humidity. The atmosphere at the time of preparing the electrolyte is preferably set to have a dew point of −40 ° C. or lower, more preferably −50 ° C. or lower. The prepared electrolyte is preferably stored under the same low humidity atmosphere.
The water content can be measured by a usual Karl Fischer water content measuring device.

The free acid content of the present invention is preferably 100 ppm or less, more preferably 80 ppm or less, and particularly preferably 60 ppm or less. The lower limit is preferably as low as possible, but it is difficult to reduce the content to 2 ppm or less in terms of cost. In the present invention, the free acid content is HF. HF may be unreacted as a raw material of the supporting electrolyte, or may be generated by decomposition of the supporting electrolyte in the presence of moisture. Therefore, purification of the supporting salt and removal of water are effective in reducing the free acid content. The free acid content is based on bromthymol blue,
It can be determined by, for example, a method of measuring by neutralization titration using a 0.1 N NaOH aqueous solution.

Hereinafter, other materials and a method for manufacturing the non-aqueous electrolyte secondary battery of the present invention will be described in detail. The positive and negative electrodes used in the nonaqueous electrolyte secondary battery of the present invention can be prepared by applying a positive electrode mixture or a negative electrode mixture on a current collector. The positive electrode or negative electrode mixture can contain a conductive agent, a binder, a dispersant, a filler, an ionic conductive agent, a pressure enhancer, and various additives, respectively, in addition to the positive electrode active material or the negative electrode material.

It is preferable that the negative electrode material used in the present invention is mainly amorphous when the battery is assembled. The term “amorphous” as used herein refers to a substance having a broad scattering band having a peak at 20 ° to 40 ° in 2θ value by X-ray diffraction using CuKα ray, and having a crystalline diffraction line. Is also good. Preferably, the strongest intensity among the crystalline diffraction lines observed at a 2θ value of 40 ° or more and 70 ° or less in X-ray diffraction using CuKα ray is broad scattering observed at a 2θ value of 20 ° or more and 40 ° or less. It is preferably not more than 500 times, more preferably not more than 100 times, particularly preferably not more than 5 times, and most preferably not having a crystalline diffraction line at the top of the band. .

The negative electrode material used in the present invention has the following general formula:
It is preferable to be represented by (2). M¹M^Two _pM^Four _qM⁶ _r General formula (2) where M¹, M^TwoAre different from Si, Ge, Sn, Pb,
At least one selected from P, B, Al, and Sb
And preferably Si, Ge, Sn, P, B, and Al.
And particularly preferably Si, Sn, P, B and Al.
M^FourIs Li, Na, K, Rb, Cs, Mg, Ca, S
at least one selected from r and Ba, preferably
Is K, Cs, Mg, Ca, particularly preferably Cs, Mg
It is. M⁶Is at least one selected from O, S, and Te
Species, preferably O, S, particularly preferably O
It is. p and q are each 0.001 to 10, preferably
From 0.01 to 5, particularly preferably from 0.01 to 2
It is. r is 1.00 to 50, preferably 1.0
0 to 26, and particularly preferably 1.02 to 6.
M ¹, M^TwoThe valence of is not particularly limited.
It may be a number or a mixture of each valence. Also M
¹, M^Two, M^FourThe ratio is M^TwoAnd M^FourIs M¹Against
Changes continuously within the range of 0.001 to 10 molar equivalents
And M⁶Quantity (general formula (2)
, The value of r) also changes continuously.

Among the compounds mentioned above, in the present invention, the case where M ¹ is Sn is preferable, and the compound represented by the general formula (3)
It is represented by

SnM ³ _p M ⁵ _q M ⁷ _r General Formula (3) In the formula, M ³ is at least one selected from Si, Ge, Pb, P, B, and Al, preferably Si, Ge,
P, B, Al, particularly preferably Si, P, B, A
l. M ⁵ is Li, Na, K, Rb, Cs, Mg,
At least one selected from Ca, Sr, and Ba;
Preferably, it is Cs or Mg, particularly preferably Mg.
M ⁷ is at least one selected from O and S, and is preferably O. p and q are each 0.001 to 10, preferably 0.01 to 5, more preferably 0.01 to 1.5, and particularly preferably 0.7 to 1.0.
5 r is 1.00 to 50, preferably 1.r
00 to 26, particularly preferably 1.02 to 6.

Examples of the negative electrode material of the present invention are shown below, but the present invention is not limited thereto. SnAl _{0.4
B 0.5 P 0.5 K 0.1 O 3.65} , SnAl 0.4 B 0.5 P 0.5
Na _0.2 O _3.7 , SnAl _0.4 B _0.3 P _0.5 Rb _0.2 O
_3.4 , SnAl _0.4 B _0.5 P _0.5 Cs _0.4 O _3.65 , Sn
Al _0.4 B _0.5 P _0.5 K _0.1 Ge _0.05 O _3.85 , SnAl
_0.4 B _0.5 P _0.5 K _0.1 Mg _0.1 Ge _0.02 O _3.83 , Sn
Al _0.4 B _0.4 P _0.4 O _3.2 , SnAl _0.3 B _0.5 P
_0.2 O _2.7 , SnAl _0.3 B _0.5 P _0.2 O _2.7 , SnA
l _0.4 B _0.5 P _0.3 Ba _0.08 Mg _0.08 O _3.26 , SnAl
_0.4 B _0.4 P _0.4 Ba _0.08 O _3.28 , SnAl _0.4 B _0.5
P _0.5 O _3.6 , SnAl _0.4 B _0.5 P _0.5 Mg _0.1 O
_3.7 ,

SnAl _0.5 B _0.4 P _0.5 Mg _0.1 F _0.2
O _3.65 , SnB _0.5 P _0.5 Li _0.1 Mg _0.1 F _0.2 O
_{3.05, SnB 0.5 P 0.5 K 0.1} Mg 0.1 F 0.2 O 3.05,
SnB _0.5 P _0.5 K _0.05 Mg _0.05 F _0.1 O _3.03 , SnB
_0.5 P _0.5 K _0.05 Mg _0.1 F _0.2 O _3.03 , SnAl _{0.4
B 0.5 P 0.5 Cs 0.1 Mg 0.1} F 0.2 O 3.65, SnB
_0.5 P _0.5 Cs _0.05 Mg _0.05 F _0.1 O _3.03 , SnB _{0.5
P 0.5 Mg 0.1 F 0.1 O 3.05} , SnB 0.5 P 0.5 Mg
_0.1 F _0.2 O ₃ , SnB _0.5 P _0.5 Mg _0.1 F _0.06 O
_3.07 , SnB _0.5 P _0.5 Mg _0.1 F _0.14 O _3.03 , SnP
Ba _0.08 O _3.58 , SnPK _0.1 O _3.55 , SnPK _0.05 M
g _0.05 O _3.58 , SnPCs _0.1 O _3.55 ,

SnPBa _0.08 F _0.08 O _3.54 , SnPK
_0.1 Mg _0.1 F _0.2 O _3.55 , SnPK _0.05 Mg _0.05 F
_0.1 O _3.53 , SnPCs _0.1 Mg _0.1 F _0.2 O _3.55 , S
nPCs _0.05 Mg _0.05 F _0.1 O _3.53 , Sn _1.1 Al _0.4
B _0.2 P _0.6 Ba _0.08 F _0.08 O _3.54 , Sn _1.1 Al _0.4
B _0.2 P _0.6 Li _0.1 K _0.1 Ba _0.1 F _0.1 O _3.65 , S
n _1.1 Al _0.4 B _0.4 P _0.4 Ba _0.08 O _3.34 , Sn _1.1
Al _0.4 PCs _0.05 O _4.23 , Sn _1.1 Al _0.4 PK _0.05
O _4.23 , Sn _1.4 Al _0.5 B _0.3 P _0.4 Cs _0.2 O
_3.5 , Sn _1.2 Al _0.4 B _0.2 P _0.6 Ba _0.08 O _3.68 ,
Sn _1.2 Al _0.4 B _0.2 P _0.6 Ba _0.08 F _0.08 O _3.64 ,
Sn _1.2 Al _0.4 B _0.2 P _0.6 Mg _0.04 Ba
_0.04 O _3.68 , Sn _1.2 Al _0.4 B _0.3 P _0.5 Ba _0.08 O
_3.58 ,

Sn _1.3 Al _0.3 B _0.3 P _0.4 Na _0.2 O
_3.3 , Sn _1.3 Al _0.2 B _0.4 P _0.4 Ca _0.2 O _3.4 ,
Sn _1.3 Al _0.4 B _0.4 P _0.4 Ba _0.2 O _3.6 , Sn
_1.4 Al _0.4 PK _0.2 O _4.6 , Sn _1.4 Al _0.2 Ba
_0.1 PK _0.2 O _4.45 , Sn _1.4 Al _0.2 Ba _0.2 PK
_0.2 O _4.6 , Sn _1.4 Al _0.4 Ba _0.2 PK _0.2 Ba
_0.1 F _0.2 O _4.9 , Sn _1.4 Al _0.4 PK _0.3 O _4.65 ,
Sn _1.5 Al _0.2 PK _0.2 O _4.4 , Sn _1.5 Al _0.4 P
K _0.1 O _4.65 , Sn _1.5 Al _0.4 PCs _0.05 O _4.63 , S
n _1.5 Al _0.4 PCs _0.05 Mg _0.1 F _0.2 O _4.63 , Sn
Si _0.5 Al _0.1 B _0.2 P _0.1 Ca _0.4 O _3.1 , SnS
i _0.4 Al _0.2 B _0.4 O _2.7 , SnSi _0.5 Al _0.2 B
_0.1 P _0.1 Mg _0.1 O _2.8 ,

SnSi _0.6 Al _0.2 B _0.2 O _2.8 , Sn
Si _0.5 Al _0.3 B _0.4 P _0.2 O _3.55 , SnSi _0.5 A
l _0.3 B _0.4 P _0.5 O _4.30 , SnSi _0.6 Al _0.1 B
_0.1 P _0.3 O _3.25 , SnSi _0.6 Al _0.1 B _0.1 P _{0.1
Ba 0.2 O 2.95, SnSi 0.6 Al} 0.1 B 0.1 P 0.1 C
a _0.2 O _2.95 , SnSi _0.6 Al _0.4 B _0.2 Mg _0.1 O
_3.2 , SnSi _0.6 Al _0.1 B _0.3 P _0.1 O _3.05 , Sn
Si _0.6 Al _0.2 Mg _0.2 O _2.7 , SnSi _0.6 Al
_0.2 Ca _0.2 O _2.7 , SnSi _0.6 Al _0.2 P _0.2 O
₃ , SnSi _0.6 B _0.2 P _0.2 O ₃ , SnSi _0.8 Al
_0.2 O _2.9 , SnSi _0.8 Al _0.3 B _0.2 P _0.2
O _3.85 , SnSi _0.8 B _0.2 O _2.9 ,

SnSi _0.8 Ba _0.2 O _2.8 , SnSi
_0.8 Mg _0.2 O _2.8 , SnSi _0.8 Ca _0.2 O _2.8 , S
nSi _0.8 P _0.2 O _3.1 , Sn _0.9 Mn _0.3 B _0.4 P
_0.4 Ca _0.1 Rb _0.1 O _2.95 , Sn _0.9 Fe _0.3 B _0.4
P _0.4 Ca _0.1 Rb _0.1 O _2.95 , Sn _0.8 Pb _0.2 Ca
_0.1 P _0.9 O _3.35 , Sn _0.3 Ge _0.7 Ba _0.1 P _0.9 O
_3.35 , Sn _0.9 Mn _0.1 Mg _0.1 P _0.9 O _3.35 , Sn
_0.2 Mn _0.8 Mg _0.1 P _0.9 O _3.35 , Sn _0.7 Pb _0.3
Ca _0.1 P _0.9 O _3.35 , Sn _0.2 Ge _0.8 Ba _0.1 P
_0.9 O _3.35

The negative electrode material is obtained, for example, by firing.
The chemical formula of the compound obtained by calcining can be calculated from inductively coupled plasma (ICP) emission spectroscopy as a measuring method, and from the weight difference of powder before and after calcining as a simple method.

The amount of light metal to be inserted into the negative electrode material of the present invention may be up to approximating the deposition potential of the light metal.
The amount is preferably from 50 to 700 mol%, more preferably from 100 to 600 mol%, per negative electrode material. It is preferable that the release amount be larger than the insertion amount. How to insert light metal
Electrochemical, chemical and thermal methods are preferred. As the electrochemical method, a method of electrochemically inserting a light metal contained in the positive electrode active material or a method of directly electrochemically inserting a light metal or an alloy thereof from a light metal is preferable. As a chemical method, there is a method of mixing or contacting with a light metal or a method of reacting with an organic metal such as butyllithium. Electrochemical and chemical methods are preferred. The light metal is particularly preferably lithium or lithium ion.

In the present invention, the general
Compounds represented by formulas (2) and (3) are mainly used as a negative electrode material.
By using as
And high discharge voltage, high capacity, high safety, current
A nonaqueous electrolyte secondary battery having excellent characteristics can be obtained.
In the present invention, particularly excellent effects can be obtained.
Is a compound containing Sn and having a valence of Sn of 2
Is used as a negative electrode material. The valence of Sn is chemical
It can be determined by a titration operation. For example, Physics
165 of Chemistry of Glasses Vol.8 No.4 (1967)
It can be analyzed by the method described on page. In addition, Sn
From night shift by solid state nuclear magnetic resonance (NMR) measurement
It is also possible to decide. For example, in wide measurement
Metal Sn (zero-valent Sn) is Sn (CH_Three )_Four 7 for
A peak appears in an extremely low magnetic field around 000 ppm
On the other hand, SnO (= divalent) is around 100 ppm,
O _Two (= 4) appears around -600 ppm. This
Knight shift is the central gold when they have the same ligand as in
Since it largely depends on the valence of Sn, which is a genus, 119 Sn-
Valence can be determined from the peak position determined by NMR measurement
Becomes

Various compounds can be included in the negative electrode material of the present invention. For example, transition metals (Sc, Ti, V, C
r, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr,
Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, lanthanoid metal, Hf, Ta, W, Re, Os, I
r, Pt, Au, Hg) and Group 17 elements of the periodic table (F, C
l) can be included. Further, it may contain dopants of various compounds (for example, compounds of Sb, In, and Nb) that increase electron conductivity. The amount of the compound to be added is 0 to 2
0 mol% is preferred.

In the present invention, any of the firing method and the solution method can be adopted as a method for synthesizing the composite oxide mainly composed of the oxides represented by the general formulas (2) and (3).

For example, the firing method will be described in detail.
¹ compound, M ² compound and M ⁴ compound (M ¹ and M ² are different from Si, Ge, Sn, Pb, P, B, Al, Sb, M
⁴ may be obtained by mixing Mg, Ca, Sr, and Ba) and firing them. Examples of the Sn compound include SnO, SnO
₂ , Sn ₂ O ₃ , Sn ₃ O ₄ , Sn ₇ O ₁₃ .H ₂ O, S
n ₈ O ₁₅ , stannous hydroxide, stannic oxyhydroxide, stannous acid, stannous oxalate, stannous phosphate, orthostannic acid, metastannic acid,
Parastannic acid, stannous fluoride, stannic fluoride, stannous chloride, stannic chloride, stannous pyrophosphate, tin phosphide, stannous sulfide, stannic sulfide, etc. Can be.

As the Si compound, for example, SiO ₂ , S
Organic silicon compounds such as iO, tetramethylsilane and tetraethylsilane, alkoxysilane compounds such as tetramethoxysilane and tetraethoxysilane, and hydrosilane compounds such as trichlorohydrosilane can be exemplified.

Examples of the Ge compound include GeO ₂ , G
Examples thereof include alkoxy germanium compounds such as eO, germanium tetramethoxide, and germanium tetraethoxide.

As the Pb compound, for example, PbO ₂ , P
bO, Pb ₂ O ₃ , Pb ₃ O ₄ , lead nitrate, lead carbonate, lead formate, lead acetate, lead tetraacetate, lead tartrate, lead diethoxide, lead diisopropoxide and the like can be mentioned.

Examples of the P compound include phosphorus pentoxide, phosphorus oxychloride, phosphorus pentachloride, phosphorus trichloride, phosphorus tribromide,
Examples include trimethyl phosphoric acid, triethyl phosphoric acid, tripropyl phosphoric acid, stannous pyrophosphate, and boron phosphate.

Examples of the compound B include boron trioxide, boron trichloride, boron tribromide, boron carbide, boric acid, trimethyl borate, triethyl borate, tripropyl borate, tributyl borate, boron phosphide, boron phosphate and the like. Can be.

Examples of the Al compound include aluminum oxide (α-alumina, β-alumina), aluminum silicate, aluminum tri-iso-propoxide, aluminum tellurite, aluminum chloride, aluminum boride, aluminum phosphide, and phosphoric acid Examples include aluminum, aluminum lactate, aluminum borate, aluminum sulfide, aluminum sulfate, and aluminum boride.

Examples of the Sb compound include diantimony trioxide, triphenylantimony and the like.

As the Mg, Ca, Sr and Ba compounds,
Each oxide, hydroxide, carbonate, phosphate, sulfate,
Nitrate, aluminum compound and the like can be mentioned.

The firing conditions are preferably a heating rate of 4 ° C. or more and 2000 ° C. or less per minute.
More preferably, it is 6 ° C. or more and 2000 ° C. or less. It is particularly preferably 10 ° C or more and 2000 ° C or less, and the firing temperature is preferably 250 ° C or more and 1500 ° C or less, more preferably 350 ° C or more and 1500 ° C or less, and particularly preferably 500 ° C or more and 1500 ° C or less. And the sintering time is 0.01 hour or more and 100
Hours or less, more preferably 0.1 hour or less.
5 hours or more and 70 hours or less, particularly preferably 1 hour or more and 20 hours or less.
Preferably ° C. at 10 ⁷ ° C. or less or more, still more preferably at 4 ° C. or higher 10 ⁷ ° C. or less, particularly preferably 6
° C. and at 10 ⁷ ° C. or less or more, particularly preferably 10 ⁷ ° C. 10 ° C. or more or less.

In the present invention, the rate of temperature rise is from 50% of the firing temperature (expressed in ° C.) to 80% of the firing temperature (expressed in ° C.).
% ", Which is the average rate of temperature increase until the temperature reaches"% ", and the term" cooling rate "in the present invention refers to" 80% of the firing temperature (° C) ".
This is the average rate of temperature decrease from the point when the temperature reaches “50% of the firing temperature (expressed in ° C.)”.

The temperature may be cooled in a firing furnace, or may be taken out of the firing furnace and put into, for example, water to cool. In addition, ceramic processing (Gihodo Publishing 1
987) Gun method described on page 217, Hammer-An
A super quenching method such as a vil method, a slap method, a gas atomizing method, a plasma spray method, a centrifugal quenching method, and a melt drag method can also be used. Alternatively, cooling may be performed using a single roller method or a twin roller method described in page 172 of the New Glass Handbook (Maruzen 1991). In the case of a material that melts during firing, a fired product may be continuously taken out while supplying raw materials during firing. In the case of a material that melts during firing, it is preferable to stir the melt.

The firing gas atmosphere is preferably an atmosphere having an oxygen content of 5% by volume or less, and more preferably an inert gas atmosphere. Examples of the inert gas include nitrogen, argon, helium, krypton, xenon, and the like.

Formulas (2) and (3) used in the present invention
The average particle size of the compound represented by 0.1 to 60 μm
Is preferably 1.0 to 30 μm, and more preferably 2.0 to 30 μm.
-20 μm is more preferred. In order to obtain a predetermined particle size, a well-known pulverizer or classifier is used. For example, mortar, ball mill, sand mill, vibrating ball mill,
A satellite ball mill, a planetary ball mill, a swirling air jet mill, a sieve, and the like are used. At the time of pulverization, wet pulverization in the presence of water or an organic solvent such as methanol can also be performed as necessary. Classification is preferably performed to obtain a desired particle size. The classification method is not particularly limited, and a sieve, an air classifier, a drainage, and the like can be used as necessary. Classification can be performed both in a dry type and a wet type.

More preferred lithium-containing transition metal oxide cathode materials used in the present invention include lithium compounds / transition metal compounds (where transition metals are Ti, V, C
It is preferable to mix and synthesize so that the total molar ratio of r, Mn, Fe, Co, Ni, Mo, and W) is 0.3 to 2.2. Particularly preferred lithium-containing transition metal oxide cathode materials used in the present invention include lithium compounds / transition metal compounds (where the transition metal is at least one selected from V, Cr, Mn, Fe, Co, and Ni). Is a total molar ratio of 0.3 to
It is preferable to synthesize them by mixing them to 2.2.

A particularly preferred lithium-containing transition metal oxide cathode material used in the present invention is Li _x QO _y (where Q is mainly, at least one of which is Co, Mn,
Transition metal containing Ni, V, Fe, x = 0.2 to 1.2,
It is preferable that y = 1.4-3). Q is Al, Ga, In, Ge, Sn, Pb, or S in addition to the transition metal.
b, Bi, Si, P, B, etc. may be mixed. The mixing amount is preferably 0 to 30 mol% based on the transition metal.

More preferred Lithium used in the present invention
Li-containing metal oxide cathode materials include Li_xCoO_Two ,
Li_xNiO_Two , Li_xMnO_Two , Li_xCo_aNi
_1-a O _Two , Li_xCo_bV_1-b O_z, Li_xCo_bFe
_1-b O_Two , Li_xMn_Two O_Four , Li_xMn_cCo_2-c O
_Four , Li_xMn_cNi_2-c O_Four , Li_xMn_cV_2-c O
_Four , Li_xMn_cFe_2-c O_Four (Where x = 0.02
1.2, a = 0.1-0.9, b = 0.8-0.98,
c = 1.6 to 1.96, z = 2.01 to 2.3).
Can be

The most preferred lithium-containing transition metal oxide cathode material used in the present invention is Li _x CoO
_{2, Li x NiO 2, Li} x MnO 2, Li x Co a N
_{i 1-a O 2, Li} x Mn 2 O 4, Li x Co b V 1-b O
_z (where x = 0.02 to 1.2, a = 0.1 to 0.
9, b = 0.9 to 0.98, z = 2.01 to 2.3). Here, the above-mentioned x value is a value before the start of charge / discharge, and increases / decreases due to charge / discharge.

The conductive carbon compound that can be used in the present invention is not particularly limited as long as it is an electron conductive material that does not cause a chemical change in the constructed battery. Specific examples include flake graphite, flake graphite, natural graphite such as earthy graphite, petroleum coke, coal coke, celluloses, sugars, high-temperature fired bodies such as mesophase pitch, and graphite such as artificial graphite such as vapor-grown graphite. Carbon blacks such as acetylene black, furnace black, ketjen black, channel black, lamp black and thermal black, asphalt pitch, coal tar, activated carbon, meso fuse pitch, polyacene and the like. Among these, graphite and carbon black are preferred.

Examples of conductive agents other than carbon include conductive fibers such as metal fibers, metal powders such as copper, nickel, aluminum and silver; conductive whiskers such as zinc oxide and potassium titanate; and titanium oxide and the like. A conductive metal oxide or the like can be used alone or a mixture thereof can be included as needed.

The amount of the conductive agent added to the mixture layer is preferably from 6 to 50% by weight, particularly preferably from 6 to 30% by weight, based on the negative electrode material or the positive electrode material. In the case of carbon or graphite, the content is particularly preferably 6 to 20% by weight.

As the binder for holding the electrode mixture used in the present invention, one of polysaccharides, thermoplastic resins and polymers having rubber elasticity or a mixture thereof can be used. Preferred binders are starch, carboxymethylcellulose, cellulose, diacetylcellulose, methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, sodium alginate,
Water-soluble polymers such as polyacrylic acid, sodium polyacrylate, polyvinylphenol, polyvinylmethylether, polyvinylalcohol, polyvinylpyrrolidone, polyacrylamide, polyhydroxy (meth) acrylate, styrene-maleic acid copolymer, polyvinyl chloride, polytetra Fluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfone (Meth) acrylates containing (meth) acrylic acid esters such as activated EPDM, polyvinyl acetal resin, methyl methacrylate, 2-ethylhexyl acrylate, etc. Acrylic acid ester copolymer, (meth) acrylic acid ester - acrylonitrile copolymer,
Polyvinyl ester copolymer containing vinyl ester such as vinyl acetate, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, polybutadiene, neoprene rubber, fluorine rubber, polyethylene oxide, polyester polyurethane resin, polyether polyurethane resin, polycarbonate Emulsions (latex) or suspensions of polyurethane resins, polyester resins, phenol resins, epoxy resins and the like can be given. In particular, polyacrylate latex, carboxymethyl cellulose, polytetrafluoroethylene, and polyvinylidene fluoride are preferred.

These binders can be used alone or as a mixture. If the amount of the binder added is small, the holding power and cohesive force of the electrode mixture is weak and the cycleability is poor, and if too large, the electrode volume increases and the volume per electrode unit volume or unit weight decreases, and further, The conductivity decreases and the capacity decreases. The amount of the binder added is not particularly limited,
It is preferably from 1 to 30% by weight, particularly preferably from 2 to 10% by weight.

The preparation of the negative electrode mixture or the positive electrode mixture paste of the present invention is preferably carried out in an aqueous system.

For the preparation of the mixture paste, first, an active material and a conductive agent are mixed, a binder (resin powder suspension or emulsion (latex)) and water are added and kneaded and mixed. , A mixer, a homogenizer, a dissolver, a planetary mixer, a paint shaker, a sand mill or the like, and a dispersing machine can be used.

The prepared mixture paste of the positive electrode active material and the negative electrode active material is mainly used after being coated (coated) on a current collector, dried and compressed. Coating can be performed by various methods, for example, 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. I can do it. The blade method, the knife method and the extrusion method are preferred. Application is
It is preferably carried out at a speed of 0.1 to 100 m / min. At this time, by selecting the above-mentioned coating method in accordance with the liquid physical properties and drying properties of the mixture paste, a good surface state of the coating layer can be obtained. The thickness, length and width of the coating layer are determined depending on the size of the battery. The thickness of the coating layer is particularly preferably 1 to 2000 μm in a compressed state after drying.

As a drying or dehydrating method for removing moisture from the pellets and sheets, generally employed methods can be used, and hot air, vacuum, infrared rays, far infrared rays, electron beams and low humidity air can be used alone or in combination. Can be used. The temperature is preferably in the range of 80 to 350C, particularly preferably in the range of 100 to 250C. The water content is preferably 2000 ppm or less in the whole battery, and is preferably 500 ppm or less in each of the positive electrode mixture, the negative electrode mixture and the electrolyte from the viewpoint of charge / discharge cycleability.

The compression of the sheet-shaped electrode mixture can be performed by a commonly used pressing method, but a die pressing method and a calender pressing method are particularly preferable. The pressing pressure is not particularly limited, but is 10 kg / cm ^{2 to 3} t / c.
m ² is preferred. The press speed of the calendar press method is
0.1 to 50 m / min is preferred. Press temperature is from room temperature
200 ° C. is preferred.

The support or current collector for the positive electrode and the negative electrode that can be used in the present invention is made of aluminum, stainless steel, nickel, titanium or an alloy thereof for the positive electrode, and copper, stainless steel, or the like for the negative electrode. Nickel, titanium,
Or, these are alloys, and are in the form of foil, expanded metal, punching metal, or wire mesh. Especially,
Aluminum foil is preferable for the positive electrode, and copper foil is preferable for the negative electrode.

The separator which can be used in the present invention is not limited as long as it has a high ion permeability, a predetermined mechanical strength, and an insulating thin film.
Fluorine polymer, cellulose polymer, polyimide, nylon, glass fiber, alumina fiber is used,
As the form, a nonwoven fabric, a woven fabric, or a microporous film is used. In particular, the material is preferably polypropylene, polyethylene, a mixture of polypropylene and polyethylene, a mixture of polypropylene and Teflon, a mixture of polyethylene and Teflon, and the form is preferably a microporous film. In particular, a microporous film having a pore size of 0.01 to 1 μm and a thickness of 5 to 50 μm is preferable.

FIG. 1 is a sectional view showing an example of a cylinder type battery. The shape of the battery can be applied to any of buttons, coins, sheets, cylinders, corners and the like. The battery is formed by inserting the electrode sheets 4 and 5 wound together with the pellets, sheets or the separator 3 into the battery can 2, electrically connecting the can and the electrodes, injecting the electrolyte 6 and sealing the battery. The inner lid body 10 provided with the ring 11 is fitted to the upper opening of the battery can 2 via the gasket 1 made of polypropylene, and the upper part of the positive electrode cap 8 also serving as the positive electrode terminal is exposed. At this time, the safety valve 7 (explosion-proof valve body) can be used as a sealing plate. Further, it is preferable to use the PTC element 9 in order to guarantee the safety of the battery.

The bottomed battery outer can that can be used in the present invention is made of nickel-plated iron steel plate or stainless steel plate (SUS304, SUS304L, SUS304N, S).
US316, SUS316L, SUS430, SUS4
44, etc.), a nickel-plated stainless steel plate (same as above), aluminum or its alloy, nickel, titanium, and copper.
It has a square tubular shape and a rectangular tubular shape. In particular, when the outer can also serves as the negative electrode terminal, a stainless steel plate or a nickel-plated iron steel plate is preferable, and when the outer can also serves as the positive electrode terminal, a stainless steel plate, aluminum or an alloy thereof is preferable.

The sheet-shaped mixture electrode is wound or folded and inserted into a can, the can and the sheet are electrically connected, an electrolyte is injected, and a battery can is formed using a sealing plate. At this time, a safety valve can be used as a sealing plate. In addition to the safety valve, various conventionally known safety elements may be provided. For example, a fuse, a bimetal, a PTC (positive temperature coefficient) element, or the like is used as the overcurrent prevention element. In addition to the safety valve, as a countermeasure against an increase in the internal pressure of the battery can, a method of making a cut in the battery can, a gasket cracking method or a sealing plate cracking method can be used. Further, the charger may be provided with a circuit incorporating measures for overcharging and overdischarging.

The entire amount of the electrolyte may be injected at one time, but it is preferable to perform the injection in two or more steps. In the case of injecting in two or more steps, each liquid may have the same composition but different compositions (for example, after injecting a non-aqueous solvent or a solution in which a lithium salt is dissolved in a non-aqueous solvent, a non-aqueous solution having a higher viscosity than the solvent) A solution in which a lithium salt is dissolved in a solvent or a non-aqueous solvent is injected). Also, in order to shorten the electrolyte injection time, the pressure of the battery can is reduced (preferably 500 to 1).
torr, more preferably 400 to 10 torr) or
Centrifugal force or ultrasonic waves may be applied to the battery can.

For the can or the lead plate, a metal or an alloy having electrical conductivity can be used. For example, metals such as iron, nickel, titanium, chromium, molybdenum, copper, and aluminum or alloys thereof are used. As 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. A conventionally known compound or mixture such as asphalt can be used as the sealing agent for sealing.

The gaskets usable in the present invention are olefin polymers, fluorine polymers, cellulosic polymers, polyimides and polyamides, and olefin polymers are preferred in view of organic solvent resistance and low moisture permeability. Propylene-based polymers are preferred. Further, it is preferably a block copolymer of propylene and ethylene.

[0083] The battery of the present invention is covered with an exterior material as necessary. Examples of the exterior material include a heat-shrinkable tube, an adhesive tape, a metal film, paper, cloth, paint, a plastic case, and the like. Further, at least a part of the exterior may be provided with a portion that changes color by heat so that the heat history during use can be recognized.

The batteries of the present invention are assembled in series and / or in parallel as necessary and stored in a battery pack. In addition to safety elements such as positive temperature coefficient resistors, thermal fuses, fuses and / or current interrupting elements, battery packs have safety circuits (voltage, temperature, current, etc. of each battery and / or assembled battery as a whole, Then, a circuit having a function of interrupting the current may be provided. In addition to the positive and negative terminals of the whole battery pack, the positive and negative terminals of each battery, the temperature detection terminals of the whole battery pack and each battery, the current detection terminals of the whole battery pack, etc. shall be provided as external terminals on the battery pack. Can also. The battery pack may have a built-in voltage conversion circuit (such as a DC-DC converter). In addition, connection of each battery
The lead plate may be fixed by welding, or may be fixed with a socket or the like so as to be easily detachable. Further, the battery pack may be provided with a display function of the remaining battery capacity, the presence or absence of charging, the number of times of use, and the like.

The battery of the present invention is used for various devices.
In particular, video movies, portable VCRs with built-in monitors, movie cameras with built-in monitors, compact cameras,
It is preferably used for a single-lens reflex camera, a film with a lens, a notebook computer, a notebook word processor, an electronic organizer, a mobile phone, a cordless phone, a razor, a power tool, a power mixer, a car, and the like.

[0086]

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 unless it exceeds the gist of the invention.

[Preparation of Positive Electrode Mixture Paste] LiCoO ₂ as a positive electrode active material was prepared as follows. A mixture of lithium carbonate and tricobalt tetroxide in a molar ratio of 3: 2 was placed in an alumina crucible, heated in air at 2 ° C./min to 750 ° C., calcined for 4 hours, and further calcined at 2 min / min. 90 ° C
The temperature was raised to 0 ° C., calcined at that temperature for 8 hours, and then pulverized to prepare LiCoO ₂ particle powder. LiCo created
The O ₂ particles have a center particle size of 5 μm, and the conductivity of a dispersion obtained by dispersing 50 g of the washed product in 100 ml of water is 0.6.
mS / m, pH was 10.1, and specific surface area by nitrogen adsorption method was 0.42 m ² / g. The LiCoO ₂ particles 2
00 g and 10 g of acetylene black were mixed with a homogenizer, followed by 8 g of an aqueous dispersion of a copolymer of 2-ethylhexyl acrylate, acrylic acid and acrylonitrile (solids concentration: 50% by weight) as a binder, and 2% by weight. A 60% aqueous carboxymethylcellulose solution was added, kneaded and mixed, 50 g of water was further added, and the mixture was stirred and mixed with a homogenizer to prepare a positive electrode mixture paste.

[Preparation of Negative Electrode Mixture Paste] SnGe _0.1
B _0.5 P _0.58 Mg _0.1 K _0.1 O _3.35 (tin monoxide 6.7
g, tin pyrophosphate 10.3 g, diboron trioxide 1.7 g,
0.7 g of potassium carbonate, 0.4 g of magnesium oxide, and 1.0 g of germanium dioxide are dry-mixed, put into an alumina crucible, and heated to 1100 ° C. at 15 ° C./min in an argon atmosphere.
And fired at 1100 ° C for 12 hours, then 10 ° C
/ Min and cooled from room temperature to room temperature, collected from the baking furnace, collected and pulverized with a jet mill (average particle size of 4.5 μm
In the X-ray diffraction method using CuKα ray, 2θ value is 2
It had a broad peak with an apex around 8 °, and no crystalline diffraction line was observed at a 2θ value of 40 ° or more and 70 ° or less. ) 200 g and 30 g of a conductive agent (artificial graphite) were mixed with a homogenizer, and 50 g of a 2% by weight aqueous solution of carboxymethyl cellulose and 10 g of polyvinylidene fluoride were added and mixed as a binder, and 30 g of water were further added and kneaded. By mixing, negative electrode mixture paste F-1 was prepared. As polyvinylidene fluoride, fine particles of about 0.1 μm were used.

The negative electrode mixture paste F-2 was prepared from 230 g of commercially available petroleum coke (PC-R, manufactured by Nippon Petrolem Co., Ltd.).
It was prepared by adding and mixing 50 g of a 2% by weight aqueous solution of carboxymethylcellulose and 10 g of polyvinylidene fluoride and 30 g of water, and further kneading and mixing.

[Preparation of Positive and Negative Electrode Sheets] The positive electrode mixture paste prepared above was coated on both sides of a 30 μm-thick aluminum foil current collector with a blade coater in an amount of 40 μm.
The coated sheet was applied at 0 g / m ² so that the thickness of the sheet after compression became 280 μm, dried, and then compression-molded by a roller press and cut into a predetermined size to prepare a belt-shaped positive electrode sheet. Further, in a dry box (dew point; dry air having a temperature of -50 ° C. or lower), dehydration and drying were sufficiently performed with a far-infrared heater to prepare a positive electrode sheet.

Similarly, the negative electrode mixture pastes F-1 and F-2
Was applied to a 20 μm copper foil current collector, and negative electrode sheets A and B each having a thickness of 90 μm after compression were prepared in the same manner as in the preparation of the positive electrode sheet.

[Electrolyte Adjustment] In an argon atmosphere, 200
80 ml of diethyl carbonate (DEC) is placed in a cc narrow-neck polypropylene container, and 20 ml of ethylene carbonate (EC) is added thereto while taking care that the liquid temperature does not exceed 30 ° C.
Was dissolved in small portions. Next, as a supporting salt, 0.469 g of LiBF ₄ and 14.43 g of LiPF were added to the mixed solvent.
₆ was dissolved little by little in the above-mentioned mixed solvent in the above-mentioned order while taking care that the liquid temperature did not exceed 30 ° C. The obtained electrolyte was a colorless and transparent liquid having a specific gravity of 1.135. Moisture is 18 ppm (measured with a MKC-210 Karl Fischer moisture meter manufactured by Kyoto Electronics Co., Ltd.), and free acid content is 2
0 ppm (with bromthymol blue as an indicator, 0.1 ppm
(Measured by neutralization titration using a specified aqueous NaOH solution). This electrolyte is designated as C-1 for comparison.

Further, an electrolyte A according to this example was prepared in the same manner as the electrolyte C-1, except that ethers were mixed according to the following Table 1 after DEC and EC. In addition, adjustment of the electrolyte
The test was carried out in dry sauce (dry air with a dew point minus 60 ° C.) using a sufficiently dehydrated chemical and container. In Table 1 below, the same supporting salt as electrolyte C-1 is described as a combination, and those having different compositions are described below the table.

[0094]

[Table 1] Composition of electrolyte Electrolyte DEC amount EC amount Added solvent type Added amount Supporting salt Water content Free acid content No. ml ml ml ppm ppm C-1 80 20 None 0 Combined 8 20 C-2 80 20 1,3-Dioxolane 0.01 Combined 8 20 A-1 80 20 Same as above 0.1 Combined 8 20 A-2 79.8 19.9 Same as above 0.3 combined 8 20 A-3 79.6 19.9 Same as above 0.5 Use 8 20 A-4 78 19.5 Same as above 2.5 Use 8 20 A-5 77.6 19.4 Same as above 3.0 Use together 8 20 A-6 76 19 Same as above 5.0 Use 8 20 A-7 74.5 18.5 Same as above 7.0 Use 8 20 A-8 95 5 Same as above 0.1 combined use 8 20 A-9 70 30 Same as above 0.1 combined use 8 20 A-10 78 19.5 Tetrahydrofuran 2.5 combined use 8 20 A-11 79.6 19.9 Tetrahydropyran 0.5 combined use 8 20 A-12 78 19.5 1,3-dioxane 2.5 combined use 8 20 A -13 78 19.5 1,4-Dioxane 2.5 combined 820 A-14 78 19.5 1,3-Dioxolane 2.5 alone * 1 820 C-3 78 19.5 Same as above 2.5 combined 60 120 C-4 72 18 Same as above 10 combined 820 C -5 80 20 None 0 alone * 1 8 20 C-6 80 20 1,3-dioxolane 0.01 alone * 1 8 20 alone * 1 is LiPF₆ Only 15.19 g was used.

[Preparation of Cylinder Battery] As shown in FIG. 1, a positive electrode sheet 5, a separator made of a microporous polypropylene film, a negative electrode sheet A (4) and a separator 3
, And this was spirally wound. The wound body was housed in a nickel-plated iron bottomed cylindrical battery can 2 also serving as a negative electrode terminal. Further, as electrolyte 6, Table 1
Was injected into the battery can 2. A battery cover 8 having a positive electrode terminal, a PTC element 9, an explosion-proof valve body 7, and the like were stacked and caulked via a gasket 1 to produce a cylindrical battery.

The battery prepared by the above method was charged and discharged under the conditions of a current density of 5 mA / cm ² , a charge end voltage of 4.1 V, and a discharge end voltage of 2.8 V, and the discharge capacity and cycle life were determined.

Table 2 shows the cycle performance (the ratio of the 300th capacity to the first charge / discharge) of each battery. The discharge capacity is shown as a relative value when battery numbers 1 and 21 are set to 100.

[0098]

Table 2 Battery No. Negative electrode sheet Electrolyte No. Discharge capacity Cycling property 1 Comparative battery AC-1 100 68 2 Same as above AC-2 100 69 3 Battery of this example A A-1 100 804 Same as above A A-2 100 82 5 Same as above A A-3 100 82 6 Same as above A A-49986 7 Same as above A A-59984 8 Same as above A A-699 829 9 Same as above A A-798 78 10 Same as above A A-8 100 74 11 Same as above A A-99997812 Same as above A A-10987313 Same as above AA-11987114 Same as above AA-12987515 Same as above AA-13987216 Same as above AA-14998217 Comparative battery A C-391 5918 Same as above AC-4966919 Same as above AC-5 100 6720 Same as above AC-6 100 6721 Same as above BC-1 100 6922 Example Battery B A-4 99 89 23 ditto B A-14 99 86 24 Comparative Battery B C-5 99 68

In Comparative Battery No. 17, the water content of the electrolyte C-3 was 60 ppm, and the free acid content was 120 ppm. In contrast, in the present example, a battery using an electrolyte having a water content of 8 ppm and a free acid content of 20 ppm was prepared. The smaller the water content and the free acid content of the electrolyte, the larger the discharge capacity and cycleability, and good results were obtained. The water content of the electrolyte is preferably 50 ppm or less, and the free acid content is preferably 100 ppm or less. However, it is difficult to control the water content to 0.5 ppm or less, and it is difficult to control the free acid content to 2 ppm or less in terms of cost. Therefore, the electrolyte has a water content of 0.5 ppm or more and 50 ppm or more.
ppm or less, and the free acid content is 2 ppm or more and 100 ppm
The following is preferred.

Comparative battery numbers 1, 2, 19, 20, 21,
In No. 24, the electrolyte contained only 0.01% by volume or less of cyclic ether. Comparative Battery No. 18 contains 10% by volume of cyclic ether in the electrolyte. On the other hand, in battery numbers 3 to 16, 22, and 23 according to the present embodiment, the electrolyte contains 0.1 to 7.0% by volume of cyclic ether. The battery according to the present embodiment has good cyclability and is good. The electrolyte preferably contains 0.1% by volume or more and 7% by volume or less of a cyclic ether. In that case, besides the cyclic ether,
The cyclic carbonate is preferably 5 to 30% by volume and the chain carbonate is preferably 60 to 90% by volume. Particularly preferably, the cyclic carbonate is 15 to 26% by volume, the chain carbonate is 71 to 85% by volume, and the cyclic ether is 0.3 to
The mixing ratio is 5% by volume.

The battery No. 16 of the present embodiment is the same as the battery of the electrolyte A-1.
In Example 4, only LiPF ₆ was used as an indicator salt. On the other hand, in the battery No. 6 according to the present example, LiBF ₄ and LiPF ₆ were used in combination as the supporting salt in the electrolyte A-4. LiBF
_The use of both LiPF ₆ and LiPF ₆ increases the cycleability and is better. The electrolyte is composed of LiBF ₄ and L as supporting salts.
it is preferred to include a iPF _6.

[0102]

As in the present invention, when the cyclic carbonate, the chain carbonate and the specific amount of the cyclic ether are used, and the electrolytic solution in which the water content and the free acid content are specified is used, the discharge capacity and the cyclability are compatible. Non-aqueous secondary batteries can be made. This effect is particularly great when a predetermined oxide is used for the negative electrode.

[Brief description of the drawings]

FIG. 1 is a sectional view of a cylinder type battery used in Examples.

[Explanation of symbols]

 Reference Signs List 1 gasket made of polypropylene 2 negative electrode can (battery can) also serving as negative electrode terminal 3 separator 4 negative electrode sheet 5 positive electrode sheet 6 nonaqueous electrolyte solution 7 explosion-proof valve 8 positive electrode cap also serving as positive electrode terminal 10 internal lid 11 ring

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Ishizuka 210, Nakanuma, Minamiashigara-shi, Kanagawa Fuji Photo Film Co., Ltd. (72) Inventor Mikihiko Kato 210, Nakanuma, Minamiashigara-shi, Kanagawa Fuji Photo Film Co., Ltd.

Claims (7)

[Claims] 1. A non-aqueous electrolyte secondary battery comprising a positive electrode and a negative electrode containing a material capable of reversibly occluding and releasing lithium, a non-aqueous electrolyte containing a lithium salt, and a separator. Chain carbonate and 0.1
It contains a cyclic ether of not less than 7% by volume and a water content of 0.5 ppm to 50 ppm and a free acid content of 2 pp as HF.
A non-aqueous electrolyte secondary battery characterized in that the concentration is not less than m and not more than 100 ppm. 2. The lithium salt contained in the non-aqueous electrolyte is Li
The non-aqueous electrolyte secondary battery according to claim 1, characterized in that it comprises a PF ₆ and LiBF _4. 3. The non-aqueous electrolyte secondary battery according to claim 1, wherein the cyclic ether is represented by the following general formula (1). Embedded image In the formula, R ¹ and R ² may be the same or different and each represent a hydrogen atom or an alkyl group having 8 or less carbon atoms. 4. The non-aqueous electrolyte secondary battery according to claim 3, wherein R ¹ and R ² of the cyclic ether are a hydrogen atom or an alkyl group having 4 or less carbon atoms. 5. The electrolyte according to claim 1, wherein the content of the cyclic carbonate is 5% by volume or more and 30% by volume or less, and the content of the chain carbonate is 60% by volume or more and 90% by volume or less. Item 5. The non-aqueous electrolyte secondary battery according to any one of Items 1 to 4. 6. The electrolyte solution has a cyclic carbonate content of 15 vol% to 26 vol%, a chain carbonate content of 71 vol% to 85 vol%, and a cyclic ether content of 0.3 vol% to 0.3 vol%. The non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein the content is not less than 5% by volume and not more than 5% by volume. 7. The non-aqueous electrolyte secondary battery according to claim 1, wherein at least one of the negative electrode materials is represented by the general formula (2). M ¹ M ² _p M ⁴ _q M ⁶ _r General formula (2) (where M ¹ and M ² are different from Si, Ge, Sn, P
at least one selected from b, P, B, Al, and Sb;
M ⁴ is Li, Na, K, Rb, Cs, Mg, Ca, S
at least one selected from r and Ba, M ⁶ is O, S,
At least one selected from Te, p and q are each 0.0
01 to 10, r represents a number of 1.00 to 50. )