JP3374124B2 - Non-aqueous electrolyte secondary battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] TECHNICAL FIELD The present invention relates to a chargeable / dischargeable cover.
Positive electrode made of oxide
Selected from oxides and carbon materials that can be stored and released
And a non-aqueous electrolyte comprising a solvent and a solute
Non-aqueous electrolyte secondary battery equipped with
It relates to improvement of the liquid. [0002] 2. Description of the Related Art Lithium using lithium as a negative electrode active material
Batteries are particularly noteworthy because of their high energy density
Has been actively researched. But
The voltage of this type of battery is as high as 3 V or more,
Are likely to occur on the surface of the positive electrode or negative electrode.
Decomposition products adhere. Therefore, batteries can be
When stored, the internal impedance of the battery rises.
Discharge characteristics may deteriorate, or in the case of secondary batteries, cycle
There are problems such as deterioration of characteristics. did
Therefore, suppressing the reactivity of the electrolyte is an
This is an important issue in practical use. Here, heretofore, it has been conventionally used as an electrolyte for this type of battery.
The organic solvent used is 1,2-dimethoxyethane
(DME), tetrahydrofuran (THF), 1,3-
Low viscosity ether solvent such as dioxolane (DOXL)
And propylene carbonate (PC), γ-butyrolact
Cyclic ester such as ton (γ-BL) or cyclic lactone
Tons, etc. are used to solve the above-mentioned problems.
For example, 2-methyl-tetrahydrofuran (2Me
-THF) and 4-methyl-1,3-dioxolane (4M
e-DOXL) etc.
It has been proposed to use substituted derivatives and the like. [0004] SUMMARY OF THE INVENTION
Even when such an electrolyte is used, the reactivity of the electrolyte is
Cannot be suppressed significantly, and as a result,
There is a problem that improvement cannot be sufficiently achieved. So
Here, the present invention aims to sufficiently suppress the reactivity of the electrolytic solution.
Cycle characteristics and storage characteristics.
To provide a non-aqueous secondary electrolyte battery
And [0005] The present invention achieves the above object.
To form a positive electrode made of a chargeable / dischargeable cobalt oxide
Electrode, lithium alloy, oxide capable of inserting and extracting lithium
And a negative electrode made of one selected from carbon materials, and a solvent
Non-aqueous electrolyte comprising: and a non-aqueous electrolyte comprising a solute
In the secondary battery, the nonaqueous electrolytic solution contains ethylene
-Carbonate, propylene carbonate, butylene carbonate
Nate, dimethyl carbonate, diethyl carbonate
At least one solvent selected from the group consisting of
The compound shown in the following and the compound shown in the chemical formula 2 were mixed at a molar ratio of 3
The mixed solute mixed in the range of 0:70 to 70:30
It is characterized by being contained. [0006] The lithium bis (alkyls)
If the solute (rhonimide) is contained in the solute,
Decomposed products and polymers form a coating on the surface of the negative and positive electrodes
Adhesion can be suppressed. Therefore, the cycle of the secondary battery
The characteristics can be improved and the battery is preserved.
Storage characteristics because the rise in internal impedance of the
Can be improved. Specifically,
is there. That is, in general, the decomposition reaction of the electrolytic solution
Promoted by products such as radicals generated by decomposition
In order to increase the stability of the electrolyte,
It is necessary to improve solute stability as well as qualitative
You. In that respect, bis (alkyl sulfo)
The cation of (honimido) has excellent stability as an ion.
It is. Therefore, highly reactive lasers even under high voltage
It is difficult to generate dicals, etc., and suppresses the decomposition reaction of the electrolytic solution.
And that is possible. Incidentally, those shown in the above chemical formula 1 and those shown in the chemical formula 2
If a mixed solute is used, storage characteristics and cycle characteristics
Not only high performance but also high rate discharge characteristics
You. This is because the solute shown in Chemical Formula 2 lacks stability
However, this is because the conductivity is high. [0009] DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] (Reference Example) FIG. 1 shows a reference example and an embodiment of the present invention.
FIG. 2 is a cross-sectional view of a flat nonaqueous electrolyte secondary battery, in which lithium
The negative electrode 2 made of an aluminum alloy is included in the negative electrode current collector 7
The negative electrode current collector 7 is ferrite-based.
Inner bottom of negative electrode can 5 made of stainless steel (SUS430)
It is fixed to the surface. The peripheral end of the negative electrode can 5 is made of polypropylene.
It is fixed inside the insulating packing 8 and the insulating packing
A positive electrode can 4 made of stainless steel is fixed to the outer periphery of the ring 8.
Have been. On the inner bottom surface of the positive electrode can 4, a positive electrode current collector 6 is fixed.
The positive electrode 1 is fixed on the inner surface of the positive electrode current collector 6.
Is defined. A positive electrode is provided between the positive electrode 1 and the negative electrode 2.
A cell made of a porous polypropylene membrane impregnated with electrolyte
The parator 3 is interposed. In the above electrolyte,
Equal volume mixing of carbonate and propylene carbonate
In the solvent, LiN (CF_Three SO_Two)_Two One mo
Used at a ratio of 1 / l. The positive electrode 1 is made of manganese as an active material.
Adhesion with oxide, acetylene black as conductive agent
With a fluororesin as an agent in a weight ratio of 85: 10: 5.
The combined product was produced by pressure molding. Also,
The dimensions of this battery are 24.0 mm in outer diameter and 3.0 mm in thickness.
is there. The battery having such a configuration is hereinafter referred to as (A1) battery.
I do. As a solute of the electrolytic solution, LiBF_Four(0.5
Mol / l) and LiN (CF_Three SO_Two) 2 (0.5 mol /
l) except that a solute mixed with l) is used.
A battery was constructed in the same manner as described above. Battery with such a configuration
Is hereinafter referred to as (A2) battery. (Comparative Example) LiBF as a solute of the electrolytic solution_Four(1 mol /
1) Except that l) is used, the battery is the same as the battery (A1) above.
Was configured. A battery having such a configuration is referred to as a (W) battery
Called. (Experiment 1) The batteries (A1), (A2) and
In the battery (W) of the comparative example, the battery was stored at 60 ° C. for 20 days.
After examining the cycle characteristics, the results are shown in FIG.
You. The experimental conditions were as follows: charge at 1.5 mA for 3 hours.
And then discharge for 3 hours at a discharge current of 1.5 mA.
When the battery voltage reaches 1.5V within the discharge time
The point was taken as the cycle life. FIG. 2 shows that the (A1) battery and the (A2) battery
Cycle characteristics after storage are significantly faster than comparative (W) batteries
It is recognized that it has been improved. This is shown below
This is probably due to the reason. That is, (W) of the comparative example
In batteries, the electrolyte solute is LiBF_Fourof
Electrolyte during storage and with the passage of cycles.
Of the polymer and the polymer on the positive and negative electrode surfaces
Decomposition products adhere. On the other hand, (A1)
Pond, (A2) Batteries have excellent stability in electrolyte solutes
LiN (CF_ThreeSO _Two)_Two[Or electrolyte
Solute is LiN (CF_ThreeSO_Two)_TwoConsisting of
The decomposition of the electrolyte is suppressed over time and over the course of the cycle.
The polymer and decomposition products on the surface of the positive and negative electrodes
Can be prevented from adhering.
You. (Experiment 2) The battery (A1) of the above reference example,
(A2) In the battery and the (W) battery of the comparative example,
Fig. 3 shows the results of examining the high-rate discharge characteristics in the early stage of the production.
Show. The experimental conditions were as follows: after each battery was fully charged, the discharge current
The condition is that the battery is discharged at 5 mA. From FIG. 3, (A2
 ) Batteries have significantly higher rate discharge characteristics than (A1) batteries
Improved, and has substantially the same performance as the (W) battery of the comparative example.
Is allowed. This is thought to be due to the following reasons.
Can be That is, in the (A1) battery, the solute of the electrolytic solution is low.
LiN (CF_ThreeS
O_Two)_Two, The high rate discharge characteristics are slightly inferior. This
On the other hand, in the case of the (A2) battery,
LiN (CF_ThreeSO_Two)_TwoNot only that, the highly conductive Li
BF_FourHigh cycle rate as well as high cycle rate
Discharge characteristics can be improved.
You. The battery (X) of the comparative example has a high rate discharge characteristic.
Although excellent, cycle characteristics are significantly reduced as described above.
Therefore, it lacks practicality. Example 1 A positive electrode, a negative electrode, and a solvent
・ Change the solute and change the solute mixing ratio to various values
Except that it was changed to (A1) of the first reference example.
A battery was produced in the same manner as the pond. [0018] Positive electrode: Cobalt oxide that can be charged and discharged Negative electrode: Chargeable / dischargeable carbon Electrolyte solvent: Propylene carbonate and dimethyl carbonate
Equal volume mixed solvent with Bonate Electrolyte solute: LiPF₆ And LiC (CF_Three SO_Two )_Three
Mixed solute with (Experiment 3) As described above, the solute ratio was changed to various values.
The initial high-rate discharge characteristics and the high
Rate discharge characteristics. FIG. 4 shows the results. The storage conditions are above
The conditions are the same as those in Experiment 1, and the experiment of high-rate discharge characteristics
The conditions are the same as those in Experiment 2. It is clear from FIG.
Like, LiPF₆ And LiC (CF_Three SO_Two )_ThreeWith
The mixing ratio is in the range of 30:70 to 70:30
Is preferred. [Second Reference Example] (Reference example) Propylene carbonate as a solvent for the electrolytic solution
And a mixture of equal volumes of dimethoxyethane and
LiN (C₆H_FiveSO_Two)_Two(Benzensulfone
An imide, in a ratio of 1 mol / 1 with respect to the solvent.
(A1) except that (dissolved) is used.
It was successful. The battery having such a configuration is referred to as (B) Battery
Called. (Comparative Example) LiN (C₆H_FiveSO_Two)_Two
Instead of LiC1O_Four(Lithium perchlorate), Li
BF_Four(Lithium tetrafluoroborate), LiPF
₆(Lithium hexafluorophosphate)
Otherwise, the configuration is the same as that of the above-mentioned reference example. In addition, each solute
Are dissolved in the solvent at a ratio of 1 mol / 1. A battery having such a configuration is described below.
(X1) battery to (X3) battery. (Experiment) Battery (B1) and batteries (X1) to (X1) of Comparative Example
3) We examined the cycle characteristics with the battery.
The results are shown in Table 1. The experimental conditions were as follows: charge current 2 mA, 4 o'clock
After charging for 2 hours, discharge for 4 hours with a discharge current of 2 mA
The condition is that when the voltage reaches 1.5 V within the discharge time, the battery
Life time. The number of samples of each battery is five. [0022] [Table 1]As is clear from Table 1, (B) the battery
Compared with the comparative example (X1) battery to (X3) battery,
It is recognized that the property has been improved. [Third Reference Example] (Reference Example) Ethylene carbonate as a solvent for the electrolytic solution
Mixed medium of propylene carbonate and dimethoxyethane
Body (mixed at a ratio of 40:40:20 by volume)
Otherwise, the configuration was the same as that of the battery (B). A battery having such a configuration is referred to as a battery (C) below.
Called. (Comparative Example) Ethylene carbonate as a solvent for the electrolytic solution
Mixed medium of propylene carbonate and dimethoxyethane
Using body (mixed at a ratio of 40:40:20 by volume)
Has the same structure as the batteries (X1) to (X3) of the second reference example.
It was successful. A battery having such a configuration is described below.
(Y1) Battery to (Y3) Battery. (Experiment) Battery (C) and Comparative Example (Y1) Battery to (Y)
3) We examined the cycle characteristics with the battery.
The results are shown in Table 2. The experimental conditions were the same as those of the second reference example.
And the number of samples for each battery is 5.
Was. [0026] [Table 2] As is clear from Table 2, (C) the battery
Compared with the comparative example (Y1) battery to (Y3) battery,
It is recognized that the property has been improved. [Fourth reference example] (Reference example) Ethylene carbonate and 2-methyl
Using an equal volume mixed medium with l-tetrahydrofuran,
LiN (CH_ThreeC₆H_FourSO_Two)_Two(Toluenesul
(B) of the second reference example, except that
The construction was the same as that of the pond. The battery having such a configuration is hereinafter referred to as (D) Battery
Called. (Comparative Example) Ethylene carbonate and 2-methyl
Other than using an equal volume mixed medium with le-tetrahydrofuran
Are the same as the batteries (X1) to (X3) of the second reference example.
Configuration. A battery having such a configuration is described below.
(Z1) Battery to (Z3) Battery. (Experiment) The battery (D) and the batteries (Z1) to (Z1) of the comparative example
3) We examined the cycle characteristics with the battery.
The results are shown in Table 3. The experimental conditions were the same as those of the second reference example.
And the number of samples for each battery is 5.
Was. [0030] [Table 3]As is apparent from Table 3, (D) the battery
Compared with the comparative example (Z1) battery to (Z3) battery,
It is recognized that the property has been improved. Here, the first
As is apparent from Reference Examples 4 to 4, the solute
Cycles can be achieved regardless of the type of solvent by using titanium bis
It is recognized that the effect of improving characteristics can be obtained. The concentration of the solute is 0.1 to 2.0 mol.
/ L, the effect of improving the cycle characteristics can be sufficiently obtained.
It has been confirmed by experiments that it can be obtained. However
However, it is preferably at least 0.5 mol / 1. Furthermore, on
In the Reference Examples and Examples, the cycle characteristics were tested.
However, the battery internal impedance
It has also been confirmed that there is an effect of suppressing the increase in the impedance. In addition, other than those shown in the examples and reference examples
The same applies when using lithium bis (alkylsulfonimide).
Experiments have also confirmed that the same effects can be obtained. [Other Matters] R shown in the following Chemical Formula 3 is the same as in the above Examples and
CF shown in Reference Example_ThreeIt is not limited to
Alkyl group, aryl group or a substituent thereof (for example,
CH_Three, C_TwoH_Five, C_TwoF_Five, CC1_Three, Benzene, tolue
N). [0034] Embedded image X shown in the following Chemical Formula 4 is the same as in the above Examples and References
It is not limited to P or the like shown in the example, but may be As, Sb, etc.
There may be. [0036] Embedded image The negative electrode is made of lithium metal or lithium alloy.
Not limited, acid capable of occluding and releasing lithium
Or a carbon material. With the solvent of the electrolyte solution
Is not limited to propylene carbonate, etc.
Butylene carbonate, diethyl carbonate, etc.
There may be. [0038] As described above, according to the present invention,
Ethylene carbonate, propylene carbonate
, Butylene carbonate, dimethyl carbonate
G, selected from diethyl carbonate
Lithium bisalkyl
Mixed with sulfonimide and highly conductive LiXFn
Mixed in a molar ratio of 30:70 to 70:30
High reactivity, even under high voltage
Difficult to generate radicals, etc., and suppresses decomposition reaction of electrolyte solution
As a result, the cycle of non-aqueous electrolyte secondary battery
Characteristics and storage characteristics can be dramatically improved, and
Also, excellent high rate discharge characteristics can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of a flat nonaqueous electrolyte secondary battery according to an embodiment. FIG. 2 is a graph showing cycle characteristics after storage in (A1) battery, (A2) battery and (W) battery of Comparative Example. FIG. 3 is a graph showing the high rate discharge characteristics of the (A1) battery, the (A2) battery, and the (W) battery of the comparative example at the initial stage of battery fabrication. FIG. 4 is a graph showing the initial high-rate discharge characteristics and the high-rate discharge characteristics after storage when the mixture ratio of the solute of the electrolytic solution is changed. [Description of Signs] 1 Positive electrode 2 Negative electrode 3 Separator

Continuation of the front page (72) Inventor Ryuji Oshita 2-5-2-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Inventor Nobuhiro Furukawa 2-5-2-5 Keihanhondori, Moriguchi-shi, Osaka (56) References JP-A-5-74479 (JP, A) JP-A-2-37673 (JP, A) Patent 3123780 (JP, B2) Patent 3316221 (JP, B2) (58) Survey Field (Int.Cl. ⁷ , DB name) H01M 10/40 H01M 6/16

Claims (1)

(57) [Claim 1] A positive electrode comprising a chargeable / dischargeable cobalt oxide, a negative electrode comprising a lithium alloy, an oxide capable of inserting and extracting lithium and a carbon material, In a non-aqueous electrolyte secondary battery comprising a non-aqueous electrolyte comprising a solvent and a solute, the non-aqueous electrolyte comprises at least one selected from ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, and diethyl carbonate. One kind of solvent and a mixed solute obtained by mixing a compound represented by the following chemical formula 1 and a compound represented by the following chemical formula 2 within a mixing molar ratio of 30:70 to 70:30 are contained. Characteristic non-aqueous electrolyte secondary battery. Embedded image Embedded image