JPH03105858A - Manufacture of nonaqueous solvent secondary battery - Google Patents

Abstract

PURPOSE:To obtain a nonaqueous solvent secondary battery which is excellent in the properties of battery capacity and charge and discharge cycle life, etc., by melting a specific crystalline compound in inactive atmosphere and then quenching the compound to form an amorphous compound, and preparing a positive electrode active material made from the amorphous compound. CONSTITUTION:A crystalline compound expressed by the expression I is melted in inactive atmosphere and is quenched to form an amorphous compound, and a positive electrode active material made from the amorphous compound is prepared. In the expression I, M is B2O3, P2O5, SiO2, Bi2O3, TeO2, WO3, MoO2, NbO2, GeO2, Ag2O, CuO, PbO, Sb2O3, SnO2, and TiO2, and x is 0.3<=x<=1 and y 0<=y<=30. Thus a nonaqueous solvent secondary battery excellent in charge and discharge cycle life property and whose discharge capacity does not decrease much is obtained.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing a non-aqueous solvent secondary battery, and in particular to a non-aqueous solvent secondary battery with an improved positive electrode active material preparation process. Relates to the manufacturing method.

(Prior art) In recent years, non-aqueous solvent batteries that use light metals such as lithium, sodium, and aluminum as negative electrode active materials have attracted attention as high-energy density batteries. [(CF)]
Primary batteries using thionyl chloride (sOcI 2 ) and the like are already widely used as power sources for calculators and watches, and as backup batteries for memories. Furthermore, in recent years, with the miniaturization and weight reduction of various electronic devices such as VTRs and communication equipment, the demand for high energy density secondary batteries as their power sources has increased, and non-aqueous solvent secondary batteries using light metals as negative electrode active materials have increased. Batteries are being actively researched.

Nonaqueous solvent secondary batteries use light metals such as lithium, sodium chloride, and aluminum for the negative electrode, and propylene carbonate (PC) and 1,2-dimethquine ethane (DME) for the electrolyte.
, γ-butyrolactone (γ-13 L') LI in a non-aqueous solvent such as tetrahydrofuran (THF)
CD Oa Li BF4, J, l As F6, L
It is composed of a dissolved electrolyte such as IPFb, and the positive electrode active materials are mainly TiS2, MO S2, V2
Compounds that undergo tobochemical reactions between lithium ε, such as 0s and V6013, have been studied.

However, as for the above-mentioned secondary batteries, only some small-capacity coin-shaped batteries are currently in practical use, and large-capacity batteries such as cylindrical batteries have not yet been put into practical use.

On the other hand, recently, vanadyl pentoxide with amorphous horizontal structures r>A
A nonaqueous solvent electrolyte using (V2 0s ) as a positive electrode active material is disclosed in JP-A-61-116758 and JP-A-81-20.
This is proposed in Publication No. 0667. When a battery is constructed by combining amorphous vanadium pentoxide with metallic lithium,
At high voltage, the LX has an energy density more than twice that of current nickel-cadmium storage batteries. ') is attracting attention because it can.

However, in non-aqueous solvent secondary batteries in which vanadium pentoxide is used as a positive electrode active material, the lithium that has entered the vanadium pentoxide during the first discharge does not completely escape from the vanadium pentoxide during the next charge, but some remains. As a result, the lithium negative electrode will be reduced by the amount remaining in the vanadium pentoxide. Further, as crystalline vanadium pentoxide is repeatedly charged and discharged, its discharge capacity decreases. On the other hand, by making vanadium pentoxide of inferior quality, the charge-discharge cycle characteristics of the positive electrode active material can be improved. However, the problem still occurs that the lithium that entered the positive electrode active material during the first discharge does not completely come out of the positive electrode active material during the next charge, but remains partially, leading to a decrease in the amount of lithium in the negative electrode. Such a decrease in the lithium negative electrode creates a gap between the lithium negative electrode and the positive electrode, and the lithium deposited during charging tends to become dendrites.

JP-A-82-178054 proposes compensating for such irreversible lithium sites by adding Li and O in advance. By such addition of L120, 1
The difference between the amount of discharge between the first and second times becomes smaller, and the charging/discharging cycle is improved.

However, even if the amount of Lt 2 O added is increased, it is still not possible to compensate for all the irreversible lithium sites.

(Problems to be Solved by the Invention) The present invention was made to solve the above-mentioned conventional problem: The purpose is to provide a manufacturing method.

[Structure of the Invention] (Means for Solving the Problems) The present invention comprises a negative electrode made of lithium or a lithium alloy, a positive electrode made of a positive electrode active material, and an electrolytic solution in which an electrolyte is dissolved in a non-aqueous solvent. In the production of nonaqueous solvent secondary batteries, the general formula (Ll.VzOs) too-y M, [where M in the formula is B203 P20SS102 B
I203 Te02 WO3Mo o2
Nb ()z Ge 02 Ag
2 0. CuO, Pb OS Sb z O
3 Sn 02T1 02 , x is 0.3≦X
f. This is a method for manufacturing a non-aqueous solvent secondary battery, which is characterized by preparing a positive electrode active material of 10% or less.

In the above formula, the blending ratio of lithium (X) '5'
If yO is less than 3, the effect of the addition cannot be fully exhibited, whereas if the lithium content exceeds 1, problems such as difficulty in handling may occur.

In the above formula, when the blending ratio (y) of M is 0, the positive electrode active material is composed only of vanadium pentoxide, but from the viewpoint of improving cycle characteristics, an oxide represented by M in the formula may be added. is valid, special i:BzOi, P20s,
St02, B1z03, M O O 2 , W O i
Adding can have a significant effect. If the blending ratio (y) of the oxide exceeds 30 mol%, the battery capacity will decrease. More preferable ratio (y) of oxide (M) is 1 to 20
It is mole%.

The crystalline compound represented by the above general formula is, for example, V20
9 powder, lithium salt powder such as lithium oxalate, and P
It is obtained by a method in which oxide powder such as No. 20 is fired in an atmosphere of an inert gas such as argon or helium at a temperature of 400° C. or higher but below the melting temperature.

When obtaining such a crystalline compound, it is desirable to perform firing in an inert gas atmosphere as in the subsequent melting and quenching.

Examples of the inert gas include argon, helium, and the like. In this case, nitrogen is excluded as an inert gas.

When melting the crystalline compound, it is desirable to melt the compound at a temperature higher than the melting temperature of the compound and lower than the decomposition temperature of the compound. Specifically, it is desirable to melt in a temperature range of 800 to 1000°C.

The rapid cooling means after melting can be produced by a liquid rapid cooling method, but is not particularly limited. When using the liquid quenching method, either a single roll method or a twin roll method may be used.

The above positive electrode is formed into a pellet shape by molding the non-quality amorphous Li V, O and containing compound powder, which is the positive electrode active material, together with a conductive material and a binder, and amorphous LI.
A sheet-like product obtained by kneading V205-containing compound powder with a conductive material and a binder, or amorphous Li V20
Examples include those in which a compound powder containing 5, a conductive material, and a binder are suspended in a suitable solvent, and the suspension is applied onto a substrate to form a coating film.

(Function) According to the present invention, the crystalline compound represented by the general formula is placed in an inert atmosphere.
V. By preparing a compound containing O, and using it as a positive electrode active material in the positive electrode, composition fluctuations in Lt V20, which occur when the crystalline compound represented by the above general formula is melted in air and rapidly cooled, can be eliminated. Therefore, charging and discharging characteristics can be significantly improved.

Further, by using the non-quality LI V20-containing compound prepared by the above method as the positive electrode active material of the positive electrode, the L-th discharge capacity can be suppressed and the degree of consumption of the lithium negative electrode can be suppressed. As a result, the gap created between the lithium negative electrode and the positive electrode can be reduced, and lithium dendrites that are deposited during charging can be suppressed.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to FIG.

Example 1 First, commercially available V20s powder and lithium oxalate (
L1 2 C2 04 ) powder and P205 powder were mixed at a molar ratio of 100:40:5, and the mixed powder was fired at 550° C. for 6 hours in an argon atmosphere. When X-ray diffraction measurements were performed on this burned product, it was found that β-L1 o. It was confirmed that the phase consisted of IV209 phase and 7-LIV209 phase. Subsequently, this fired product was melted at 850° C. for 2 hours in an argon atmosphere, then rapidly cooled by a twin roll method, and the obtained scaly material was crushed to prepare an amorphous LIXV205 compound powder. This powder is
It was confirmed by line diffraction that it was a non-quality material. Subsequently, 80% by weight of the non-quality Li A strip-shaped positive electrode with a diameter of 200 cm was produced.

Next, a cylindrical nonaqueous solvent secondary battery shown in FIG. 1 was assembled using the positive electrode. That is, numeral 1 in FIG. 1 is a bottomed cylindrical stainless steel container which also serves as a negative electrode terminal and has an insulator 2 disposed at the bottom. An electrode group 3 is housed in this container l. This electrode group 8 includes the positive electrode 4 produced by the method described above.
, a separator 5, and a negative electrode B are laminated in this order, and the strip is spirally wound so that the negative electrode B is located on the outside. The separator 5 is formed from a polypropylene porous film.

The negative electrode 6 has a shape in which a band-shaped lithium foil is crimped onto a nickel expanded band metal current collector.

Further, the container 1 contains an electrolytic solution of 2-methyltetrahydrofuran in which lithium hexafluoroarsenate (LIASF6) of 1.5 molar concentration is dissolved. An insulating paper 7 with an opening in the center is placed on the electrode group 3. Further, an insulating sealing plate 8 is provided at the upper opening of the container 1 in a liquid-tight manner by caulking the container 1, and a positive electrode terminal 9 is fitted in the center of the insulating sealing plate 8. has been done.

This positive electrode terminal 9 is connected to the positive electrode 4 of the electrode group 3 via a positive electrode lead IO. Note that the negative electrode 6 of the electrode group 3
is the negative terminal via the negative lead (not shown).
It is connected to the.

Example 2 Commercially available V2 0q powder and lithium oxalate (Ll 2
C2 0a) powder and P2 0% powder in a molar ratio of 10
The mixed powder was mixed at a ratio of 0:30:5, and the mixed powder was fired at 550°C for B hours under an argon atmosphere.The fired product was melted at 850°C for 2 hours under an argon atmosphere, and then rapidly cooled by a twin roll method. The obtained scaly material was pulverized to prepare a non-quality LI V205 compound powder, and a non-aqueous battery having the same structure as in Example 1 was used, except that a positive electrode containing this amorphous LI VzOs compound powder as the positive electrode active material was used. A solvent secondary battery was assembled.

Comparative Example 1 Commercially available V205 powder and lithium oxalate (L1
2 C2 04 ) powder and P2 09 powder were mixed at a molar ratio of 100:40:5, and the mixed powder was fired at 550°C for 6 hours in an argon atmosphere.
After melting in air at 850°C for 2 hours, it was rapidly cooled by a twin-roll method, and the resulting scaly material was crushed to obtain amorphous Ll.
v, o, compound powder is prepared, and this amorphous LI
A non-aqueous solvent secondary battery having the same structure as in Example 1 was assembled, except that a positive electrode containing V,05 compound powder as the positive electrode active material was used.

Comparative Example 2 Commercially available V 2 0 s powder and p, o, powder in a molar ratio of 9
Other than using a positive electrode in which the positive electrode active material was an amorphous V20s compound powder mixed at a ratio of 5:5, melted at 1200 ° C. for 2 hours under an argon atmosphere, and then rapidly cooled by a twin roll method. A non-aqueous solvent battery having the same configuration as in Example 1 was assembled.

Therefore, for the non-aqueous solvent secondary batteries of Examples 1 and 2 and Comparative Examples 1 and 2, the battery voltage was 2.0 at a current of 800 mA.
The relationship between the charge/discharge cycle and the discharge capacity was investigated by repeating the charge/discharge cycle of discharging the battery until it reached OV and then charging it with a current of 100 mA until the battery voltage reached 3.5 V.
A characteristic diagram shown in FIG. 2 was obtained.

Note that A to D in FIG. 2 are characteristic lines of the non-aqueous solvent secondary batteries of Examples 1 and 2 and Comparative Examples 1 and 2, respectively.

6 As is clear from Figure 2, the battery of Comparative Example 2 shows a fairly large discharge capacity of about 1000mA h in the first discharge, but about 550mA in the second discharge.
h discharge capacity, which means that lithium was reduced by about 450 mA h. On the other hand, in the batteries of Examples 1 and 2, the first discharge had a discharge capacity of about 1330 mAh, and the second discharge had a discharge capacity of about [i00 mAh, and the decrease in lithium was about 30 mAh.
It can be seen that the loss of lithium is very small compared to the battery. Furthermore, it can be seen that the cycle life is greatly improved compared to the battery of Comparative Example 1, which uses a positive electrode active material that has deteriorated in quality in air. Furthermore, it can be seen that there is little drop in discharge capacity even at the beginning of the charge/discharge cycle, and a stable discharge capacity can be obtained.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to provide a method for manufacturing a non-aqueous solvent secondary battery with less decrease in discharge capacity and excellent charge/discharge cycle life characteristics.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a cylindrical nonaqueous solvent secondary battery assembled in a large example of the present invention, and FIG. 2 is a nonaqueous solvent secondary battery of Examples 1 and 2 and Comparative Examples 1 and 2. FIG. 3 is a characteristic diagram showing the relationship between the number of charge/discharge cycles and discharge capacity. l... Stainless steel container, 3... Electrode group, 4... Positive electrode, 5... Separator, B... Negative electrode, 8... Sealing plate, 9... Positive electrode terminal.

Claims (1)

[Claims] In the production of a non-aqueous solvent secondary battery comprising a negative electrode made of lithium or a lithium alloy, a positive electrode made of a positive electrode active material, and an electrolyte solution in which an electrolyte is dissolved in a non-aqueous solvent, the general formula (Li_xV_2O_5)_1_0_0_-_yM, [
However, M in the formula is B_2O_3, P_2O_5, SiO
_2, Bi_2O_3, TeO_2, WO_3, MoO
_2, NbO_2, GeO_2, Ag2O, CuO, P
bO, Sb_2O_3, SnO_2, TiO_2, x is 0.3≦x≦1, y is 0≦y≦30] is melted in an inert atmosphere and rapidly cooled to form an amorphous compound. 1. A method for producing a non-aqueous solvent secondary battery, which comprises preparing a positive electrode active material made of a purified compound.