JP3281701B2 - Non-aqueous electrolyte battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte battery comprising a positive electrode, a negative electrode containing lithium as an active material, and a non-aqueous electrolyte, and more particularly to an improvement of the non-aqueous electrolyte. is there.

[0002]

2. Description of the Related Art A non-aqueous electrolyte battery using, for example, lithium as a negative electrode active material has attracted attention as a battery having a high energy density, and has been actively studied. Generally, in this type of battery, ethylene carbonate, propylene carbonate,
Simple substances and mixtures of butylene carbonate, vinylene carbonate, 1,2-dimethoxyethane, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, tetrahydrofuran, 1,3-dioxolane and the like are used. As a solute dissolved therein, a fluorine-containing lithium salt, for example, lithium hexafluorophosphate (LiPF ₆ ), is mainly used because of its good electrical conductivity and environmental safety. .

[0003] Further, as a negative electrode material of this kind of battery, lithium metal or an alloy capable of inserting and extracting lithium,
A carbon material is mainly used to constitute a secondary battery.

When a battery having such a non-aqueous electrolyte comprising a solvent and a solute is stored in a charged state, the non-aqueous electrolyte is decomposed by some action of the solute, and the capacity of the battery after storage is reduced. Tends to decrease.
Further, when a carbon material such as graphite or coke is used as the negative electrode material, the above tendency is further enhanced. In particular, in a secondary battery, a cathode reduction reaction during charging causes a reaction between an electrode material, a solute, and a solvent,
This creates a situation where the non-aqueous electrolyte can be easily decomposed. As a result, the non-aqueous electrolyte is degraded, and the characteristics of the battery are rapidly reduced. Therefore, suppressing self-discharge during storage is an important issue in putting this type of battery to practical use.

The reason is presumed as follows. That is, lithium hexafluorophosphate, which is a fluorine-containing lithium salt as a solute, is used in the electrolytic solution, and there is a possibility that hydrogen fluoride (HF) as an impurity that must be removed originally remains. is there. Further, lithium hexafluorophosphate as a solute may be decomposed to generate hydrogen fluoride (HF) due to severe conditions such as charging and discharging of the secondary battery and changes over time during storage. Thus, when hydrogen fluoride (HF) is present in the battery,
The organic solvent constituting the non-aqueous electrolyte may be decomposed or adversely affect charge and discharge.

[0006]

SUMMARY OF THE INVENTION The present invention provides a non-aqueous electrolyte battery having excellent storage characteristics by suppressing the deterioration of the electrolyte used in such a battery, for example, the reaction between the electrolyte and the negative electrode material. Is what you do. Another object is to improve the charge / discharge cycle characteristics of a secondary battery.

[0007]

In order to achieve the above object, the present invention provides a positive electrode, a negative electrode using lithium as an active material,
Solutes mainly composed of fluorine-containing lithium salt and ethylene car
Bonate, propylene carbonate, butylene carbonate
, Vinylene carbonate, 1,2-dimethoxyethane,
Dimethyl carbonate, diethyl carbonate, ethyl
Methyl carbonate, tetrahydrofuran, 1,3-diox
Non-aqueous electrolysis consisting of a solvent selected from the group consisting of solan
A non-aqueous electrolyte battery comprising:
Add calcium carbonate, calcium salt, to the solution.
It is characterized by the following.

[0008] The amount of calcium carbonate added is
0.01% to 3.0% by weight based on the weight of the aqueous electrolyte
Within the range , the effect of addition is observed. And especially preferably, the range of 0.5% by weight to 2.0% by weight is optimal from the viewpoint of storage characteristics and cycle characteristics of this kind of nonaqueous electrolyte battery.

The lithium salts containing fluorine include lithium tetrafluorophosphate (LiPF ₆ ) and lithium trifluoromethanesulfonate (LiCF ₃ S).
O ₃ ) and lithium trifluoromethanesulfonimide (LiN (CF ₃ SO ₂ ) ₂ ) can be used.

Here, a metal oxide containing manganese, cobalt, nickel, vanadium and niobium can be used as the positive electrode.

As the negative electrode, it is possible to use lithium metal or an alloy capable of inserting and extracting lithium, for example, a lithium-aluminum alloy, a carbon material, for example, coke and graphite.

[0012]

When a non-aqueous electrolyte containing calcium carbonate is used among calcium salts , the added calcium carbonate
Effect of calcium salts to stabilize the non-aqueous electrolyte solution is
Will be noticeable. This mechanism can be considered as follows.
That is, the calcium salt reacts with hydrogen fluoride (HF) to produce stable calcium fluoride (CaF ₂ ), thereby enclosing fluorine ions. Further, the reaction between the negative electrode material kept active in the charged state and the fluorine ions is suppressed.

As a result, hydrogen fluoride (H
It can be considered that the possibility of the influence of the fluorine ions generated from F) being suppressed and the decomposition of the non-aqueous electrolyte solution being suppressed. In this manner, the storage characteristics and cycle characteristics of the battery can be improved.

[0014]

Embodiments of the present invention will be described below in detail. (Embodiment 1) FIG. 1 shows a half sectional view of a cylindrical non-aqueous secondary battery as an embodiment of the battery of the present invention. In the figure, positive electrode 1
Uses lithium-containing cobalt dioxide heat-treated in a temperature range of 700 ° C. to 900 ° C. as an active material, and mixes the lithium-containing cobalt dioxide, carbon powder as a conductive agent, and fluororesin powder as a binder with 85:10: After mixing at a weight ratio of 5 and then applying the mixture to a current collector, the mixture was heat-treated at 100 ° C. to 150 ° C. to produce a mixture. on the other hand,
The negative electrode 2 was prepared by mixing graphite (graphite) as a carbon material and a fluororesin powder as a binder in a weight ratio of 85:15, and then applying this mixture to a current collector.
It was prepared by heat treatment at a temperature of 150C to 150C. A separator 3 impregnated with a non-aqueous electrolyte, which is a key point of the present invention, is interposed between the positive electrode 1 and the negative electrode 2 to constitute a spiral electrode body. This electrode body is inserted into the battery can 4 also serving as a negative electrode terminal. A negative electrode conductor 5 is connected to the negative electrode 2 via one end. The negative electrode conductor 5 is electrically welded to the inner can bottom of the battery can 4 so as to be electrically connected to the battery can 4. On the other hand, a positive electrode conductor 6 is connected to the positive electrode 1 and is electrically connected to a battery cover 7 also serving as a positive electrode terminal. This battery cover 7 is interposed via an insulating packing 8 made of polypropylene.
It is insulated from the battery can 4 and seals the battery can 4.

As an electrolytic solution, a mixed solvent of ethylene carbonate (EC) and 1,2-dimethoxyethane (DME) (volume ratio of 5: 5) was mixed with hexafluorophosphorus, which is a fluorine-containing lithium salt as a solute. Lithium oxide (Li
PF ₆ ) was dissolved at a rate of 1 mol / l. Here, a battery of the present invention having an outer diameter of 13.8 mm and a height of 48.9 mm was prepared using a non-aqueous electrolyte in which calcium carbonate as a calcium salt was added at a ratio of 1.0% by weight to the electrolyte. A was prepared.

On the other hand, as a comparative example, a similar battery was manufactured using an electrolyte solution to which calcium carbonate was not added.

Using these batteries, the cycle characteristics of the batteries were compared. The experimental conditions at this time were as follows: each battery had a charging current of 40
After charging to a final voltage of 4.1 V at 0 mA, a discharge current of 2
The battery was discharged at 00 mA for 5 hours.
A battery that has reached 75 V has a cycle life. The result is shown in FIG. FIG. 2 shows the number of cycles (times) of the battery on the horizontal axis and the discharge capacity (mAh) of the battery on the vertical axis.

Thus, it can be understood that the battery A of the present invention has an increased cycle life and improved cycle characteristics as compared with the comparative battery X.

Next, using the battery A of the present invention and the comparative battery X, the storage characteristics of the batteries were compared. The experimental conditions at this time were
The fully charged battery is stored at 60 ° C. for 10 days, and the discharge capacity (mAh) of the battery is measured.

The results are shown in Table 1. Table 1 shows the initial discharge capacity (mAh) of the battery and the discharge capacity after storage (mAh).
h).

[0021]

[Table 1]

From this, it can be understood that the battery A of the present invention has a larger discharge capacity after storage than the comparative battery X, and a decrease in capacity due to storage is suppressed.

Accordingly, it can be understood that the battery A of the present invention has excellent cycle characteristics and storage characteristics by adding calcium carbonate. (Example 2) A battery having the same configuration as the battery A of the present invention in Example 1 was prepared, and the amount of the calcium salt added to the non-aqueous electrolyte, ie, the amount of calcium carbonate, was changed. The discharge capacities were compared. The experimental conditions at this time were
The fully charged battery is stored at 60 ° C. for three months, and the discharge capacity (mAh) of the battery is measured.

FIG. 3 shows the result. FIG. 3 shows the addition amount (% by weight) of calcium carbonate, which is a calcium salt, on the horizontal axis and the discharge capacity (mAh) after storage of the battery on the vertical axis. From these results, the addition amount of calcium carbonate was 0.01% by weight to 3. % by weight based on the weight of the non-aqueous electrolyte .
The effect of addition was observed in the range of 0% by weight , and reduction in battery capacity after storage was suppressed. The range of 0.5% by weight to 2.0% by weight is particularly suitable from the viewpoint of maintaining a large discharge capacity of the battery after storage. And
The addition of 1.0% by weight based on the non-aqueous electrolyte is optimal because it maximizes the discharge capacity of the battery.

Example 3 A mixed solvent of propylene carbonate (PC) and 1,2-dimethoxyethane (DME) was used as an electrolytic solution (in a volume ratio of 5:
Batteries similar to the battery A of the present invention and the comparative battery X of Example 1 were produced except that 5) was used, and were referred to as a battery B of the present invention and a comparative battery Y, respectively.

A battery using calcium iodide as a calcium salt was used as Reference Battery C.

Using these batteries, the cycle characteristics of the batteries were compared. The experimental conditions at this time are the same as in the first embodiment. The result is shown in FIG.

From this, the battery B of the present invention can be referred to as the reference battery C and the reference battery C.
It can be understood that the cycle life is increased and the cycle characteristics are improved as compared with the comparative battery Y.

In the above embodiment, ethylene carbonate and 1,2- as the organic solvent constituting the non-aqueous electrolyte were used.
A mixed solvent of dimethoxyethane and a mixed solvent of propylene carbonate and 1,2-dimethoxyethane were exemplified, but these alone, butylene carbonate, vinylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, tetrahydrofuran, 1,3-dioxolane , And mixtures thereof.

[0030]

As described above, a calcium salt is added to a non-aqueous electrolyte containing a solute mainly containing a fluorine-containing lithium salt.
By adding certain calcium carbonate, the storage characteristics and the cycle characteristics of this type of non-aqueous electrolyte battery can be improved, and its industrial value is extremely large.

[Brief description of the drawings]

FIG. 1 is a half sectional view of the battery of the present invention.

FIG. 2 is a diagram showing the relationship between the discharge capacity of a battery and the number of cycles.

FIG. 3 is a diagram showing the relationship between the amount of calcium carbonate added and the discharge capacity after storage of a battery.

FIG. 4 is a diagram showing the relationship between the discharge capacity of a battery and the number of cycles.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 4 Battery can 5 Negative current collector 6 Positive current collector 7 Battery cover 8 Insulation packing

Continuation of the front page (72) Inventor Yuji Yamamoto 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Inside Sanyo Electric Co., Ltd. (72) Inventor Koji Nishio 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Inside Electric Co., Ltd. (72) Inventor Toshihiko Saito 2-5-5, Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (56) References JP-A-4-62764 (JP, A) JP-A-4- 284372 (JP, A) JP-A-5-315006 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 10/40

Claims (5)

(57) [Claims] A positive electrode and a negative electrode using lithium as an active material
And a solute mainly composed of a fluorine-containing lithium salt and ethylene
Carbonate, propylene carbonate, butylene car
Bonate, vinylene carbonate, 1,2-dimethoxy eta
Dimethyl carbonate, diethyl carbonate,
Tyl methyl carbonate, tetrahydrofuran, 1,3-di
Non-aqueous system consisting of a solvent selected from the group consisting of oxolane
A non-aqueous electrolyte battery comprising:
Add calcium carbonate, a calcium salt, to the electrolyte
Non-aqueous electrolyte battery. 2. The method according to claim 1, wherein the fluorine-containing lithium salt is
Lithium fluorophosphate (LiPF ₆ ), trifluoromethane
Lithium sulfonate (LiCF ₃ SO ₃ ) and lithium trifle
Oromethanesulfonimide (LiN (CF ₃ SO ₂ ) ₂ )
Being at least one selected from a group.
The non-aqueous electrolyte battery according to claim 1. 3. The non-aqueous electrolytic solution according to claim 3 , wherein
Added in the range of 0.01% to 3.0% by weight based on the liquid
2. The non-aqueous electrolyte battery according to claim 1, wherein: 4. The method according to claim 1 , wherein the calcium carbonate is a non-aqueous electrolyte.
0.5% to 2.0% by weight based on the liquid
4. The non-aqueous electrolyte battery according to claim 3, wherein: 5. The method according to claim 1, wherein the negative electrode is made of a carbon material.
The non-aqueous electrolyte battery according to claim 1, wherein: