JPH02234350A - Positive pole of non-aqueous electrolyte battery - Google Patents

Abstract

PURPOSE:To obtain a non-aqueous electrolyte battery with a long service life by laminating a second positive pole primarily made up of a positive-pole active material selected from among gamma-MnO2, beta-MnO2, etc., on the surface of a first positive pole mainly consisting of a positive-pole active material can posed of lambda-MnO2. CONSTITUTION:A portion which is in contact with an electricity collector side on the surface of a first positive pole mainly consisting of lambda-MnO2 is covered with a second positive pole primarily consisting of manganese dioxide other than lambda-MnO2 such as gammaMnO2 and betaMnO2. A negative pole which is formed by pressure-applying metallic lithium to a negative-pole electricity collector and a positive pole are stacked in layers via a separator impregnated with a non-aqueous electrolyte and then they are sealed up in a case to obtain a button-shaped non-aqueous electrolyte lithium battery. This battery is characterized in its initial voltage maintained low, long discharge time and sufficient smoothness. In this manner, it is possible to obtain a battery with prolonged discharge time even at relatively low initial voltage and flatness.

Description

DETAILED DESCRIPTION OF THE INVENTION <<Industrial Application Field>> The present invention relates to a non-aqueous electrolyte battery such as a lithium battery, and particularly relates to a technique for improving discharge characteristics by improving a positive electrode.

<<Prior art>> 7-MnO. , β-Mno2, V6 013.
Non-aqueous electrolyte batteries using V20, MoS2, TiS2, etc. alone or in combination as positive electrode active materials are known. Batteries using these active materials have discharge characteristics depending on their characteristics, but in general, the flatness of the voltage is poor, and the voltage may drop stepwise or gradually during discharge. It is recognized that this decreases.

By the way, there is a technique using λ-M n 0 2 as a new positive electrode active material to replace these existing positive electrode active materials.

This λ-M n O 2 is, for example,
As shown in Publication No. 1, the known substance LiMn204
This positive electrode active material is based on a novel form of manganese dioxide produced by acid treatment of 100%, and is named based on the specific diffraction pattern and relative intensity of the peaks obtained by X-ray diffraction.

And the activity of a battery using this cathode active material, especially in its early stages, is different from that of other common naturally or artificially produced 7-Mn02. β-Mn02, γβ-Mn
It has significantly higher voltage characteristics than batteries using O 2 1 or other metal oxides as positive electrode active materials.

<<Problems to be solved by the invention>> However, in batteries using this positive electrode active material, the initial voltage is too high compared to other batteries, which may actually lead to destruction of the semiconductor, and the potential decreases during discharge. Because it falls in steps, it is considered unsuitable as a power supply battery for driving existing semiconductors, and despite its high characteristics, it has been difficult to put it into practical use.

The present inventors investigated extending the discharge life by utilizing the high voltage characteristics of λ-M n O 2 .

Then, on the surface of the first positive electrode whose main ingredient is a positive electrode active material made of λ-M n O 2 , a well-known 7
-Mn02, β-Mn02, 7β-Mn0
2, V6 013, Mo S2, T i S
By laminating a second positive electrode whose main ingredient is a positive electrode active material selected from 2 and bringing it into contact with the TEPCO body, the discharge characteristics are close to those of low-potential active materials and have good flatness. We discovered that it is possible to obtain a non-aqueous electrolyte battery with a sufficiently long discharge life.

This invention was made based on the above knowledge,
The present invention aims to provide a positive electrode for a non-aqueous electrolyte battery that has good voltage flatness and a larger capacity than conventional ones.

<<Means for Solving the Problems>> In order to achieve the above object, the present invention provides at least part or all of the surface of the first positive electrode made of λ-Mn02, a conductive agent, and a binder that contacts the aggregate side. , γM
nO2, βM n 0 2, etc.
The second positive electrode is coated with a positive electrode active material made of a mixture of one or more of manganese dioxide, transition metal oxides, and sulfides other than , and a conductive agent and a binder.

As shown in Japanese Patent Publication No. 58-3441, the above-mentioned λ-M n O 2 is obtained by using LiMn204, a known substance, as a starting material, suspending it in water, adding an acid, and p.
Stabilize the temperature to below H2.5, then wash until neutral.
It is obtained by filtering and drying the obtained MnO2 product, and as shown in the same publication, the X-ray diffraction pattern and the relative intensity of the X-ray diffraction peak are different from that of the existing γ-Mn.
It has different characteristics from O2, β-M n 02, and γβ-M n 0 2.

Said 7-Mn02, β-Mn02, 7β-Mn02
, Vb 013, V2 0s , MOS2 , TiS2
are known positive electrode active materials, and these are used alone or in combination as positive electrode active materials.

A non-aqueous electrolyte battery using the above positive electrode active material is assembled as follows.

That is, the above-mentioned λ-M n O is used as a positive electrode active material, and a conductive material such as graphite and a binder such as polytetrafluoroethylene are mixed in a known mixing ratio, and a disc-shaped material of an appropriate thickness is formed by press molding. While forming the first positive electrode, the positive electrode active material selected from the above-mentioned γ-Mn02 etc. is similarly mixed with a conductive material and a binder to form a second positive electrode, and then the two are laminated and pressed to form a two-layer structure. Alternatively, a second positive electrode may be pressed into a laminated state on top of the previously formed first positive electrode to form a two-layer positive electrode. Next, the positive electrode is vacuum-dried at 240° C., and then a net-shaped positive electrode current collector is crimped onto the surface of the positive electrode active material such as γ-M n O 2 .

Meanwhile, metallic lithium is pressure-bonded to the negative electrode current collector.

Next, this metallic lithium negative electrode and positive electrode are laminated via a separator impregnated with a non-aqueous electrolyte, and the positive and negative electrode assembly is placed inside the battery case in contact with a battery case consisting of a positive electrode can and a negative electrode plate. By sealing, a button-shaped non-aqueous electrolyte lithium battery is obtained.

<<Function>> According to the non-aqueous electrolyte battery having the above configuration, its discharge characteristics are maintained as low as the discharge characteristics when a known positive electrode active material is used at the initial voltage, and λ-M n 02 alone It was found that the discharge time was longer than that of the positive electrode active material, and sufficient smoothness could be obtained.

Therefore, it is presumed that the known positive electrode active material on the side that is in contact with the positive electrode current collector is mainly involved in the discharge reaction.

Although λ-M n 0 2 does not directly participate in this discharge reaction, it charges the amount consumed by the discharge reaction,
It is presumed that this eliminates stepwise changes during discharge, lengthens the discharge time, and converts the high voltage of λ - M n O 2 into battery capacity.

<<Effects of the Invention>> As described above, according to the non-aqueous electrolyte battery of the present invention, the discharge time can be prolonged while maintaining a relatively low initial voltage as in the case of using a conventionally known positive electrode active material. , flatness can be obtained, and characteristics suitable as a power source for driving a semiconductor can be obtained.

<<Example>> Specific examples will be described below. However, this invention is not limited only to the examples.

Example l. Mo is a known positive electrode active material in combination with λ-Mn02.
b, to form a two-layer positive electrode as follows,
A CR2016 type battery was created using this positive electrode.

■Second positive electrode: MOO3 powder 8 parts by weight Graphite powder 1 // PTEF (binder) 1 After mixing a total of 10 parts by weight or more, press molding to a diameter of 15
Then, a disk-shaped positive electrode with a thickness of 0.21 Is was formed.

■First positive electrode λ-MnO2 powder 8 parts by weight Graphite powder 1 PTEF (binder) 1 After mixing a total of 10 parts by weight or more, a disk-shaped positive electrode with a diameter of 15 mm and a thickness of 0.5 mm is stacked on top of ■. Press molded into a
A two-layer positive electrode with a total thickness of 0.7 am (240°C
After vacuum drying), the surface of the ■ side was pressed onto a net-like aggregate.

On the other hand, a metal lithium plate with a thickness of 0.2 mm was punched out to form a negative electrode with a diameter of 15 mm, which was crimped to a negative electrode current collector, and this negative electrode and the positive electrode were connected to PC-DME, Li C 1 041
mo 1/j! The layers are stacked with a separator made of polypropylene nonwoven fabric impregnated with a non-aqueous electrolyte, and each current collector is in contact with the positive electrode can and the negative electrode plate, and the positive electrode can is attached to the negative electrode plate via a gasket. The crimping was completed and the CR2016 type button battery was completed.

Comparative example 1. Using the same production procedure, the positive electrode active material was made of λ-MnO. Single batteries, Mob batteries, and single CR2016 type button batteries were manufactured.

And Example 1. As a result of discharging the battery C according to the present invention manufactured in 1 and the batteries A and B of the comparative example at a constant current of 1 mA and setting the final voltage to 2 V, the discharge characteristics shown in FIG. 1 were obtained.

In the figure, battery A in which the positive electrode active material is λ-M n O 2 alone has a high initial voltage of 4 V, and after 30 to 40 hours of discharge, the voltage decreases stepwise and reaches the final voltage after 65 hours.

In addition, battery B, which is a single M003, has an initial discharge voltage of 3V, which is normal for this type of battery, but there is a stepwise drop after 20 to 30 hours, and after that, the voltage gradually decreases until it stops after 60 hours. becomes voltage.

On the other hand, the initial voltage of the battery obtained in Example 1 is almost the same as that of battery B, and after that, the voltage is maintained higher than that of battery B, and the voltage is gradually lowered while maintaining a smooth state. The final voltage was about 75 hours, indicating that the discharge time was longer than any other battery.

Here, to explain in detail the battery reaction of this example, λ-
In the discharge of M n O 2, a difference in crystal structure is observed between the reaction at 4V and the reaction at 3V, and a slight increase in the lattice constant from cubic to cubic is observed at 4V (in this case, Li In contrast, at 3V, a large change from a cubic crystal filled with Li to a tetragonal crystal occurs at the A site (in this case, the Li intercalation site is the A site). The location where the site is to be accessed is designated as site B.

), this phenomenon was confirmed by X-ray diffraction, and λ−M n
It is presumed that the two-stage discharge curve of O 2 is due to the above-mentioned difference in the activity of the crystals. According to Example 1, M
oO3 has a discharge characteristic with a flat portion at a discharge voltage of 2.5 to 2.3V. The reaction takes place between the layers of Mo03.
is intercalated, Mob, +L i” +e−
→Mob, (L i)・・・・・・・・・■It is thought that it becomes stable in an electrically neutralized state.

Therefore, in a state where M o O s is in contact with the current collector as in the present invention, the generated voltage is expressed by equation (2).

However, Mob, is in contact with λ-M n O 2, and due to the difference in activity between M o O , and λ-M n O , (λ-M n O 2 has higher activity than M o O , ), Li is A of λ-M n O 2 with high activity.
Move sequentially to the site. After that, lithium will enter the B site, and the discharge will end. As a result, MoO,
The activity is recovered by the removal of Li.

While lithium moves to A and B sites, the voltage is Mo03
, and the high potential part is from Mo03 to L
It is used to extract L, and M00 increases by that capacity, which is thought to make voltage flatness and high capacity possible.

Example 2. A net-like current collector was prepared in advance and fixed to the inner bottom of the positive electrode can, and a positive electrode mixture mixed in the following composition ratio was applied to the current collector, and then vacuum-dried at 250°C for 5 hours. ,
A second positive electrode having a thickness of 20 μm was molded.

10% water glass solution 50 parts by weight graphite powder
5 //M o O i
4.5'' Total: 100 parts by weight The first positive electrode was prepared using the same recipe as in Example 1, molded into a 0.7 mm shape, and crimped onto the second positive electrode.

FIG. 2 shows the discharge characteristics of a battery using the positive electrode of this example, and almost the same characteristics as in Example 1 were obtained.

In addition, in this invention, it can be fully estimated that the same effect as described above will be obtained by a combination of other known positive electrode active materials not exemplified and λ1M n 0 2 or the like.

[Brief explanation of drawings]

FIGS. 1 and 2 are graphs showing the discharge characteristics of a battery according to the present invention, a conventional positive electrode active material, and a battery using λ-M n O 2 as a positive electrode. Figure 1 Patent patent applicant Fuji Electrochemical Co., Ltd. Representative
People Patent Attorney Kensuke Kazuiro Patent Attorney Miyabi Matsumoto
Figure 2 Discharge time (hr) −

Claims (1)

[Claims] (1) Manganese dioxide other than λ-MnO_2, such as γMnO_2 and βMnO_2, and transition metal oxides, such as γMnO_2 and βMnO_2, 1. A positive electrode for a nonaqueous electrolyte battery, characterized in that the positive electrode is coated with a second positive electrode comprising a positive electrode active material made of a mixture of one or more of sulfides and sulfides, a conductive agent, and a binder.