JPH07118315B2 - Non-aqueous electrolyte secondary battery - Google Patents

Description

TECHNICAL FIELD The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly to improvement of a negative electrode material thereof.

2. Description of the Related Art Conventionally, it has been known to use lithium, sodium, aluminum or the like as a negative electrode active material in this type of non-aqueous electrolyte secondary battery. Moreover, in order to prevent dendrites from being generated in such a negative electrode active material, Cd, Al,
It is known to use fusible alloys containing Bi, Pb, Sn, In, etc.

When forming a negative electrode with a metal simple substance such as lithium, sodium, and aluminum, dendrite may be generated depending on the type of electrolyte, and the cycle life may be shortened. In the case where lithium is the negative electrode, this dendrite is generated from the active point of the lithium particle interface, and the dendrite is also active and immediately reacts with the electrolytic solution to be inactivated. Therefore, the negative electrode using a single metal has a short cycle life due to the generation of dendrite and the extra consumption of the active material due to inactivation.

When fusible gold or the like is used for the negative electrode, the negative electrode active material is occluded in the alloy and dendrite does not occur. It is also known that it exhibits characteristics that do not depend much on the type of electrolyte. However, when lithium is used as the negative electrode active material, the saturated storage amount of the alloy, including lithium, is only about 1/3 of the capacity density of 2062 mAh / cm ^{3 for} the lithium single metal. In addition, when an alloy is used for the negative electrode, the electric potential is higher by about 0.2 to 0.8 V than that of the lithium metal alone, so that the battery voltage decreases conversely and the energy density decreases.

Problems to be Solved by the Invention When such a conventional configuration is used, that is, when the negative electrode is charged and discharged using a single metal such as Li, Na, Al, dendrite is generated depending on the type of the electrolytic solution and short-circuited with the positive electrode. In addition, the surface of the dendrite is so active that it reacts with the electrolytic solution, and the deactivation proceeds rapidly, which shortens the cycle life of the battery.

In addition, an alloy is used for the negative electrode, and Li ⁺ , Na ⁺ , Al
^When occluding and releasing ⁺ etc., the cycle life does not change much depending on the type of electrolyte, but the amount of active material that can be held in the alloy is 1/3 times that of a single metal in unit volume conversion.

At the same time, the alloy holding the negative electrode active material is 0 compared to the case of a single metal.
The potential is high at about 2 to 0.8 V, and the voltage of the battery drops accordingly, resulting in a smaller energy density.

The above problems can be raised.

The present invention solves such problems, and an object thereof is to improve the energy density by increasing the cycle life and capacity of the battery.

Means for Solving the Problems At least one metal selected from the group consisting of Pb, Bi, Sn, In, As, Sb, and Al at a concentration of 1% by weight or less is added to the alkali metal as the negative electrode active material. The added one is used as a negative electrode material.

Action Since the negative electrode using the negative electrode material within the scope of the present invention shows the same potential and capacity density as in the case where the negative electrode is the active material single metal depending on the concentration added, the battery voltage is higher than when the alloy is used and Since the capacity is large, the battery has a high energy density.

In addition, active points do not concentrate on the particle interface due to the additive, and uniform active points are generated on the entire surface of the negative electrode. At the same current density, dendrite does not occur unlike the negative electrode formed of a single metal. Therefore, it becomes possible to manufacture a battery having a long cycle life.

Example The present invention is to make a negative electrode alkali metal such as lithium metal not less than the melting point and not more than the boiling point, in which 1% by weight or less of at least one of Pb, Bi, Sn, In, As, Sb, Al is mixed. ,
After melting so as to be dispersed, it is cooled. In this embodiment, the case where Pb is used among the additives will be described with reference to FIGS.

FIG. 1 shows a partial cross-sectional view of a battery having a diameter of 20 mm and a total height of 1.6 mm used for implementing the present invention. In the figure, reference numeral 1 denotes the negative electrode of the present invention, which is fixed by pressure to a stainless steel negative electrode current collector 2 formed on the inner surface of a stainless steel sealing plate 3. 4 is a stainless steel case, 5 is a titanium positive electrode current collector, 6 is a positive electrode mixture using molybdenum trioxide as a positive electrode active material, 7 is a polypropylene (hereinafter abbreviated as PP) separator having fine pores, 8
Is a PP impregnation material, and 9 is a PP gasket.

The composition of the positive electrode is, by weight, M ₀ O ₃ 100, carbon black 15, fluororesin binder 15, and is weighed to have a capacity of 20 mmAh. The positive electrode current collector 5 formed on the inner surface of the case 4
The one molded in the case was used.

The electrolyte used was propylene carbonate (Pc) in which 1 mol / l lithium perchlorate (LiClO ₄ ) was dissolved.

The negative electrode is made of various additive concentrations of lithium with a thickness of 200 μm and a diameter of 1
The one processed to 5 mmφ was used.

The voltage of the battery 24 hours after the sealing of the battery was the same as that of the battery in which lithium single metal was incorporated as the negative electrode. Further, there was no difference due to the metals listed in the present invention as additives.

However, when the additive concentration exceeded the range of the present invention, the battery voltage dropped and approached that using the alloy.

FIG. 2 shows the cycle characteristics when the negative electrode of the present invention was applied to the battery shown in FIG. Charge / discharge current is both 1mA, cut voltage at charge is 3.0V, cut voltage at discharge is
It was set to 1.0V.

In the figure, A is an additive concentration of 1% by weight, B is 0.5% by weight, and C is 0.1%.
% By weight, and D is the one using a lithium single metal.

It can be seen from FIG. 2 that the cycle life of the battery is longer than that of D using the lithium single metal. The reason why the cycle life is slightly different depending on the concentration of the additive is that the abundance of points is different in the activity depending on the concentration of the additive.

FIG. 3 is a charge / discharge curve at the 10th cycle of the battery shown in FIG. The charge / discharge conditions are the same as above.

In the figure, E is the additive concentration of 1% by weight, F is Li-Al (composition L
i: Al50: 50atomic%) alloy processed to the same size,
G is a single lithium metal. From this figure, it can be seen that there is no difference in the discharge pressure as compared with the case where E of the present invention G using lithium single metal. Moreover, the one using the alloy of F
It can be seen that the voltage is lower than E and G, and therefore the energy density is small.

EFFECTS OF THE INVENTION As is apparent from the above description, according to the present invention, a non-aqueous electrolyte secondary battery of high industrial value having characteristics of higher energy density and longer cycle life than conventional ones is provided. Can be provided.

[Brief description of drawings]

FIG. 1 is a partial sectional view of a battery according to an embodiment of the present invention,
FIG. 2 is a diagram showing cycle characteristics of the battery, and FIG. 3 is a diagram showing charge / discharge curves of the battery. 1 ... Negative electrode, 2 ... Negative electrode current collector, 3 ... Sealing plate.

Front page continuation (72) Inventor Akikatsu Morita 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Yukio Nishikawa, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (1)

[Claims] 1. A non-aqueous electrolytic solution containing an alkali metal ion,
In a battery with a chargeable / dischargeable positive electrode and an alkali metal negative electrode, lead (Pb), bismuth (B
i), tin (Sn), indium (In), arsenic (As), antimony (Sb), aluminum (Al) at least one metal selected from the group is characterized by mixing less than 1 wt% Non-aqueous electrolyte secondary battery.