JP3133321B2 - Non-aqueous battery - Google Patents

Description

The present invention relates to nonaqueous primary and secondary batteries using lithium or a substance capable of storing lithium as a negative electrode active material, and particularly to a positive electrode for a positive electrode. It is about improvement.

(B) Conventional technology Non-aqueous primary batteries using lithium as a negative electrode active material and a non-aqueous electrolyte have the advantages of high voltage, high energy density, excellent low-temperature characteristics, low self-discharge rate, and the like. It is widely used as a power source for small electric devices or portable small electronic devices, or as a power source for computer memory backup.

As a positive electrode active material of these non-aqueous primary batteries, manganese dioxide or carbon fluoride has conventionally been used as a typical one, and manganese dioxide is particularly excellent in storage stability,
It has the advantage of being abundant in resources and inexpensive.

On the other hand, a non-aqueous secondary battery in which this kind of battery can be repeatedly charged and discharged for use has been developed. As the negative electrode active material of this non-aqueous secondary battery, in addition to lithium metal, a lithium alloy using a metal that can be alloyed with lithium, such as aluminum, or a carbon material obtained by intercalating lithium is known. I have. Also, as a positive electrode active material,
Manganese dioxide containing Li ₂ MnO ₃ (JP-A-63-114064)
Manganese dioxide (see Japanese Patent Application Laid-Open No.
-235158), vanadium oxide, cobalt oxide and the like have been proposed, and some non-aqueous secondary batteries combining these negative and positive electrodes have been put to practical use.

By the way, the above-mentioned small electric devices and small electronic devices are further miniaturized, and accordingly, the non-aqueous primary batteries for power supply are also required to be miniaturized, that is, to have high capacity and high energy density. is there.

In addition, the characteristics of non-aqueous secondary batteries that are currently in practical use are still insufficient, and there is a demand for higher capacity and higher energy density.

(C) Problems to be Solved by the Invention In the conventional non-aqueous battery described above, the problem is that the energy density of manganese dioxide of the positive electrode is insufficient for miniaturization, and the charge / discharge cycle characteristics are also insufficient. was there.

The problem to be solved by the present invention is, in view of such a point,
It is to improve the discharge capacity and discharge voltage of manganese dioxide of the positive electrode, to improve the capacity and energy density of a non-aqueous battery, and to improve charge / discharge cycle characteristics.

(D) Means for Solving the Problems The present invention uses lithium or a material capable of storing lithium as a negative electrode active material, a manganese oxide containing lithium, a mixture of manganese dioxide and a lithium salt, Obtained by heat treatment at a temperature of 150 to 430 ° C and this lithium-containing manganese oxide (specific surface area 30 m ² / g or less)
In a non-aqueous battery in which the positive electrode active material is electrochemically charged to form a positive electrode active material, the positive electrode active material has peaks in both the vicinity of 2θ = 37 ° and the vicinity of 2θ = 38 ° in the X-ray diffraction diagram by CuKα. It had.

It is preferable that the above-mentioned positive electrode active material is mainly used, and a substance whose electrode potential is more noble during charging than the main positive electrode active material is added to the main positive electrode active material as an auxiliary positive electrode active material. In this case, the secondary positive electrode active material is desirably Li _x CoO ₂ (0 <x ≦ 1) or Li _x Mn ₂ O ₄ (0 <x ≦ 1) having a spinel structure.

(E) Action In the above structure, the crystal structure of the lithium-containing manganese oxide obtained by heat-treating manganese dioxide and a lithium salt depends on the heat treatment temperature. For example, at 150 to 300 ° C., X-ray diffraction by CuKα In the figure, 2θ = 22
リ チ ウ ム, 31.5 ゜, 37 ゜, 42 ゜, and 55 ゜, lithium-containing manganese oxides with peaks were obtained.
At 300 to 430 ° C., a manganese oxide containing Li ₂ MnO ₃ is obtained.

Such a lithium-containing manganese oxide can be used as it is as a positive electrode active material, but shows a higher discharge capacity and a higher discharge voltage by being electrochemically charged.

If such a lithium-containing manganese oxide is used as a main positive electrode active material and a sub-positive electrode active material having a noble electrode potential during charging is added to the main positive electrode active material, the charge / discharge cycle characteristics are also improved.

(F) Examples Hereinafter, the present invention will be described with reference to the drawings for some examples.

[Example 1] Lithium hydroxide and manganese dioxide were mixed at a molar ratio of 1: 2, and heat-treated in air at 250 ° C for 20 hours to obtain 2θ = 22 °, 31.5% by X-ray diffraction with CuKα.
Lithium-containing manganese oxides having peaks near {, 37}, 42 °, and 55 ° are obtained.

This material, acetylene black as a conductive agent, and a fluororesin as a binder were mixed at a weight ratio of 85: 10: 5 to form a positive electrode mixture, and the positive electrode mixture was subjected to a force of ² t / cm ² . Press to form a 20mm diameter.

Thereafter, the pressure-formed mixture is heat-treated at 250 ° C. in vacuum to form a positive electrode.

On the other hand, the negative electrode is formed by punching a lithium plate having a predetermined thickness into a diameter of 20 mm.

FIG. 1 shows a half section of a flat non-aqueous electrolyte secondary battery assembled using the above-mentioned positive electrode and negative electrode, wherein 1 and 2 are a stainless steel positive electrode can and a negative electrode can, which are polypropylene. Isolated by an insulating packing 3 made of stainless steel.

Reference numeral 4 denotes a positive electrode which is the gist of the present invention.
Are pressed into contact with the positive electrode current collector 5 fixed to the inner bottom surface.

Reference numeral 6 denotes a negative electrode which is pressed against a negative electrode current collector 7 fixed to the inner bottom surface of the negative electrode can 2.

Reference numeral 8 denotes a separator made of a microporous thin film made of polypropylene, and lithium perchlorate in a mixed solvent of propylene carbonate and dimethoxyethane as an electrolytic solution.
Mole / dissolved was used.

 The dimensions of the battery were 24.0 mm in diameter and 3.0 mm in thickness.

A battery assembled in this way and charged to 4.3 V with a current of 3 mA is referred to as a battery A1 of the present invention. The amount of electricity charged at this time was 60 mAh.

[Example 2] Lithium hydroxide and manganese dioxide were mixed at a molar ratio of 1: 2.
And heat-treated in air at 375 ° C. for 20 hours to obtain a manganese oxide containing Li ₂ MnO ₃ .

Thereafter, a battery was assembled by forming a positive electrode and a negative electrode in the same manner as in Example 1 and charged to 4.3 V at a current of 3 mA to obtain a battery A2 of the present invention. The amount of electricity charged at this time is 50
mAh.

[Example 3] Lithium hydroxide and manganese dioxide were mixed at a molar ratio of 1: 2, and heat-treated in air at 150 ° C for 20 hours to obtain 2θ = 22 °, 31.5 ° by X-ray diffraction with CuKα. Three
A lithium-containing manganese oxide having peaks near 7 °, 42 ° and 55 ° is obtained. Thereafter, similarly to the first embodiment, a conductive agent and a binder were mixed and molded under pressure, and subjected to a heat treatment at 150 ° C. in a vacuum to obtain a positive electrode. A battery A3 according to the present invention assembled using the positive electrode into the battery configuration shown in FIG. 1 and charged to 4.3 V with a current of 3 mA. The amount of electricity charged at this time was 60 mAh.

[Comparative Example 1] A battery assembled in the same configuration and in the same process as in Example 1 described above, and which does not perform charging after assembly is referred to as Comparative Battery B1.

[Comparative Example 2] A battery assembled in the same configuration and in the same process as in Example 2 but not charged after the assembly is referred to as Comparative Battery B2.

Comparative Example 3 A battery assembled in the same manner as in Example 1 except that lithium hydroxide was not added to the positive electrode and only manganese dioxide was heat-treated at 250 ° C. to obtain a positive electrode active material, and other configurations and steps were the same as in Example 1 above. By charging to 4.3V with a current of 3mA, the comparative battery B
Got three. At this time, the amount of electricity charged was 0 mAh.

Comparative Example 4 A comparative battery B4 was obtained without assembling and charging after assembling in the same configuration and process as in Comparative Example 3 described above.

Comparative Example 5 Lithium hydroxide and manganese dioxide were mixed at a molar ratio of 1: 2, and heat-treated at 125 ° C. in air for 20 hours. After that, the heat treatment temperature of the pressure-formed positive electrode in vacuum is 125 ° C.
A battery was assembled by forming a positive electrode and a negative electrode in the same manner as in Example 1 except that
The battery charged up to is referred to as a comparative battery B5. The amount of electricity charged at this time was 30 mAh.

FIG. 2 shows the X-ray diffraction patterns of the positive electrodes of the batteries A1 to A3 of the present invention and the comparative batteries B1 to B5, respectively. Of these diffraction diagrams
A1, A2, A3, B3, and B5 are all batteries that have been charged after assembly. In the X-ray diffraction diagram shown in FIG. 2, a peak is observed near 2θ = 37 ° in all the batteries. However, peaks near 2θ = 38 ° are seen from A1 to
Only A3 and B5, and other batteries do not show this peak.

The batteries charged after assembling the comparative batteries B1 and B2 correspond to the batteries A1 and A2 of the present invention.

Further, the comparative battery B3 using only the manganese dioxide as the positive electrode active material by heat treatment cannot charge the positive electrode at the time of charging after assembling the battery. Therefore, in the X-ray diffraction diagram of FIG. There is almost no difference from B4. Moreover, both B3,
B4 has a peak near 2θ = 37 °, but 2θ =
There is no peak near 38 ゜.

In addition, when the lithium salt and manganese dioxide were calcined at 125 ° C., fine white powder, which was considered to be an unreacted lithium salt, was observed. However, in the X-ray diffraction pattern of the positive electrode active material of the comparative battery B5 produced by electrochemically charging the same, no peaks that seemed to be lithium salts were found, so it seems that unreacted lithium was in a small amount. .

As in the batteries A1 to A3 of the present invention, the crystal structure of a substance obtained by heat-treating manganese dioxide and a lithium salt when the lithium-containing manganese oxide is charged is not confirmed, but the second It is clear that the X-ray diffraction diagram by CuKα shown in the figure has peaks near 2θ = 37 ° and 2θ = 38 °.

In addition, since all the peaks have a wide half width, and particularly a peak near 37 ° is higher, a peak near 38 ° looks just like a shoulder of a peak near 37 °.

FIG. 3 shows the batteries A1 to A3 of the present invention and the comparative batteries B1 to B5 each having a length of 3 m.
3 shows a discharge characteristic curve when discharging is performed to 2.0 V at A. Here, batteries A1, A2, and A3 of the present invention having positive electrodes charged with lithium-containing manganese oxides are comparative batteries B1, and B2 using lithium-containing manganese oxides without charging, or positive electrodes of only manganese dioxide. It is apparent that the battery B4 has a larger discharge capacity and a higher voltage at the initial stage of discharge than the battery B3 charged with the battery B4.

Further, the battery A3 of the present invention prepared by calcining a lithium salt and manganese dioxide at 150 ° C. and electrochemically charging the calcined lithium salt and manganese dioxide.
Has the same discharge capacity and discharge voltage as the batteries A1 and A2 of the present invention, but the comparative battery B5 in which the heat treatment temperature is changed to 125 ° C. has a small discharge capacity, which is because the heat treatment temperature is as low as 125 ° C. It is considered that the water removal from the positive electrode was insufficient.

Next, FIG. 4 shows that a battery similar to that of Example 1 was assembled using lithium-containing manganese oxide having a different specific surface area as a positive electrode active material, and then 4.3 mA at a current of 3 mA.
The figure shows the blister amount of the battery itself when charged to V as data.

As is clear from this figure, when a battery using a lithium-containing manganese oxide having a specific surface area of more than 30 m ² / g as a positive electrode active material is charged, the blister of the battery rapidly increases. This is considered to be caused by the fact that when the specific surface area of the lithium-containing manganese oxide is large, the reactivity with the electrolytic solution increases, so that the electrolytic solution is decomposed during charging.

In the above X-ray diffraction diagram by CuKα, 2θ = 3
The method for obtaining a lithium-containing manganese oxide having a peak near 7 ° and 38 ° is not limited to only this example, and as a lithium salt used, lithium nitrate or lithium phosphate can be applied. , The mixing ratio of lithium salt and manganese dioxide is 1 by the molar ratio of Li and Mn.
The range of 0:90 to 70:30 is desirable.

If the heat treatment temperature is lower than 150 ° C., the firing reaction between the lithium salt and manganese dioxide does not proceed sufficiently, and if the heat treatment temperature is higher than 430 ° C., manganese dioxide is decomposed. Moreover, the specific surface area of the lithium-containing manganese oxide obtained here is desirably 30 m ² / g or less in order to suppress the decomposition of the electrolytic solution.

Further, the voltage for charging the lithium-containing manganese oxide obtained by the heat treatment of the lithium salt and manganese dioxide can also be selected at an arbitrary value.

The lithium-containing manganese oxide of the present invention has reversibility to charge and discharge, as can be seen from the fact that it is obtained by charging a lithium-containing manganese oxide obtained by heat-treating a lithium salt and manganese dioxide. In addition to the application as the positive electrode active material of the nonaqueous primary battery shown in the examples, versatility as a positive electrode active material of a nonaqueous secondary battery can be expected.

[Example 4] Lithium hydroxide and manganese dioxide were mixed at a molar ratio of 1: 2, and heat-treated at 250 ° C for 20 hours in the air to obtain 2θ = 22 °, 31.5 °, 37 ° by X-ray diffraction using CuKα. , 42
Lithium-containing manganese oxide having a peak near {, 55 _} is obtained, and LiCoO as Li _x CoO ₂ (0 <x ≦ 1) where the electrode potential during charging is more noble than this manganese oxide
₂ is added in an amount of 10 wt% to form a positive electrode active material.

Acetylene black as a conductive agent and a fluororesin as a binder were mixed with this in a weight ratio of 85: 10: 5,
After forming the positive electrode mixture under pressure at ² t / cm ² , heat treatment is performed at 250 ° C. in vacuum to obtain a positive electrode mixture.

The negative electrode is obtained by punching a lithium plate having a predetermined thickness to a diameter of 20 mm.

A battery obtained by charging this battery to 4.3 V with a current of 3 mA is referred to as battery A4 of the present invention.

[Example 5] Spinel in which lithium carbonate and manganese dioxide are mixed at a molar ratio of 1: 4, and heat-treated at 850 ° C for 20 hours in air, whereby the electrode potential at the time of charging is higher than that of the lithium-containing manganese oxide. Li _x Mn ₂ O _{4 of} structure (0 <x ≦ 1)
To obtain LiMn ₂ O ₄ having a spinel structure.

A battery A5 of the present invention was produced in the same manner as in Example 4, except that LiMn ₂ O ₄ obtained as described above was added instead of LiCoO ₂ in Example 4.

[Comparative Example 6] A comparative battery B6 (same as the battery A1 of the present invention in Example 1 above) was prepared in the same manner as in Example 4 except that LiCoO ₂ was not added.

Comparative Example 7 A comparative battery B7 was produced in the same manner as in Example 4 except that only LiCoO ₂ was used as the positive electrode active material.

Comparative Example 8 A comparative battery B8 was produced in the same manner as in Example 4 except that only LiMn ₂ O ₄ having a spinel structure was used as the positive electrode active material.

FIG. 5 shows the currents of batteries A4 and A5 of the present invention and comparative batteries B6 to B8.
The graph shows changes in the discharge capacity with respect to the number of cycles when discharging to 2.5 V at 3 mA and charging to 4.3 V at 3 mA.

The batteries A4 and A5 of the present invention can be used up to 64 cycles and 61 cycles, respectively, whereas the comparative battery B7 has 55 cycles, the comparative battery B8 has reduced by 50 cycles, and the comparative battery B6 has an extremely low 23 cycles. You can see that there is. Further, by comparing the electrodes A4 and A5 of the present invention with the comparative battery B6, it is clear that A4 and A5 have a larger number of cycles than the comparative battery B6. As described above, the comparative batteries B7 and B8 have a small discharge capacity, and the comparative battery B6 has a rapid deterioration of the charge / discharge cycle. In addition, when the battery after the completion of the charge / discharge cycle was disassembled, it was observed that the dissolved manganese was precipitated on lithium as the negative electrode in the comparative battery B6, but was not observed in the other batteries of the present invention and the comparative battery. .

Further, according to FIG. 5, Li _x CoO ₂ (0 <x ≦ 1) and Li _x
Although the discharge capacity of Mn ₂ O ₄ (0 <x ≦ 1) is inferior to the case of only the lithium-containing manganese dioxide having a peak at 2θ = 37 °, 38 °, the former has a higher potential at the time of discharge, and At the time of charging, the electrode potential is about 3.8 to 4.5 V with respect to lithium, and at about 4.3 V, no dissolution of cobalt or manganese is observed. Therefore, by adding Li _x CoO ₂ or Li _x Mn ₂ O ₄ to the lithium-containing manganese dioxide as the main positive electrode active material, Li _x CoO ₂ , Li _x Mn ₂ O rather than dissolution of manganese during overcharge
The charging reaction of ₄ occurs preferentially, and dissolution of manganese can be suppressed. Further, since Li _x CoO ₂ and Li _x Mn ₂ O ₄ are also used during the discharge reaction, the discharge capacity of the entire active material does not decrease so much.

(G) Effect of the Invention As described above, the present invention relates to a non-aqueous battery using lithium or a material capable of storing lithium as a negative electrode active material, wherein a mixture of manganese dioxide and a lithium salt is used in an amount of 150 to 4%.
Heat treatment at a temperature of 30 ° C. to obtain the lithium-containing manganese oxide, and by electrochemically charging the lithium-containing manganese oxide to form a positive electrode active material, the discharge capacity and discharge voltage of the battery are reduced. Can be improved.

Further, it is assumed that the positive electrode active material has peaks in both the vicinity of 2θ = 37 ° and the vicinity of 2θ = 38 ° in the X-ray diffraction diagram by CuKα, and the electrode potential of the lithium-containing manganese dioxide is higher than this. If LiCoO ₂ and LiMn ₂ O ₄ are added, the charge / discharge cycle characteristics are improved.

[Brief description of the drawings]

1 is a half sectional view of the battery of the present invention, FIG. 2 is an X-ray diffraction diagram of the positive electrode of the battery of the present invention and the comparative battery, FIG. 3 is a discharge characteristic diagram of the battery of the present invention and the comparative battery, and FIG. FIG. 5 is a graph showing the relationship between battery flatness when a flat battery using lithium-containing manganese oxide having various specific surface areas as a positive electrode active material is charged, and FIG. 5 shows charge / discharge cycle characteristics of the battery of the present invention and a comparative battery FIG. 1 ... Positive electrode can, 2 ... Negative electrode can, 3 ... Insulating packing,
4. Positive electrode, 5 ... Positive electrode current collector, 6 ... Negative electrode, 7 ... Negative electrode current collector, 8 ... Separator, A1-A5 ... Battery of the present invention, B1-B8 ... Comparative battery.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-114064 (JP, A) JP-A-1-235158 (JP, A) JP-A-1-272051 (JP, A) JP-A-61-164 17424 (JP, A) JP-A-62-145652 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 4/36-4/62 H01M 10/40

Claims (5)

(57) [Claims] 1. A non-aqueous battery using lithium or a material capable of storing lithium as a negative electrode active material and a lithium-containing manganese oxide as a positive electrode active material, wherein a mixture of manganese dioxide and a lithium salt is 150-430 ° C
A non-aqueous battery, wherein the lithium-containing manganese oxide is obtained by heat-treating at a temperature of, and the lithium-containing manganese oxide is electrochemically charged to obtain a positive electrode active material. 2. The positive electrode active material according to claim 1, wherein the positive electrode active material has peaks both in the vicinity of 2θ = 37 ° and in the vicinity of 2θ = 38 ° in the X-ray diffraction pattern by CuKα. Non-aqueous battery. 3. The non-aqueous system according to claim 2, wherein the positive electrode active material is obtained by electrochemically charging the lithium-containing manganese oxide having a specific surface area of 30 m ² / g or less. battery. 4. The method according to claim 1, wherein the positive electrode active material is used as a main positive electrode active material, and a substance having a higher electrode potential during charging than the main positive electrode active material is added as an auxiliary positive electrode active material. The non-aqueous battery according to claim 1. 5. The method according to claim 1, wherein the auxiliary cathode active material is Li _x CoO ₂ (0 <x ≦
1) or Li _x Mn ₂ O ₄ having a spinel structure (0 <x ≦
The non-aqueous battery according to claim 4, which is 1).