JPH08115728A - Lithium primary battery - Google Patents

Abstract

PURPOSE: To enhance low temperature discharge performance by using surface modified manganese dioxide containing 1-15 atomic percent of lithium as a positive active material and specific solvent and solute as a nonaqueous electrolyte. CONSTITUTION: Electrolytic manganese dioxide whose impurity content is preferably small and a lithium compound such as lithium hydroxide are mixed, and the mixture is baked at 150-400 deg.C to obtain surface modified manganese dioxide for a positive active material. The content of lithium in the active material obtained is 1-15 atomic percent. A mixed solvent of 20-80 volume percent of a carbonate such as ethylene carbonate 80-20 volume percent of 2- dimethoxyethane is used in a nonaqueous electrolyte. Lithium trifluoromethanesulfonate or lithium hexafluorophosphate is used as a solute. By lithium formed on the surface of manganese dioxide particle, wettability to a specific nonaqueous electrolyte is enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium primary battery, and more particularly to improvement of a positive electrode active material, a solvent and a solute of a non-aqueous electrolyte for the purpose of improving low temperature discharge characteristics thereof.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
Manganese dioxide is used as a positive electrode active material of a lithium primary battery. However, manganese dioxide has a poor positive electrode wettability with a non-aqueous electrolyte, so that the effective reaction area of the positive electrode is small. Therefore, the conventional lithium primary battery has a problem that the discharge characteristic at low temperature (low temperature discharge characteristic) is not good.

As a result of earnest studies to solve this problem, the present inventors have used a non-aqueous electrolyte consisting of a specific solvent and solute and modified the surface of manganese dioxide by a predetermined means. It has been found that the poor wettability between the manganese dioxide and the non-aqueous electrolyte can be eliminated if the quality is improved.

The present invention has been made on the basis of such findings, and an object of the present invention is to provide a lithium primary battery having excellent low temperature discharge characteristics.

[0005]

A lithium primary battery according to the present invention (a battery according to the present invention) for achieving the above object comprises a positive electrode, a negative electrode using metallic lithium or a lithium alloy as an active material, a solute and a solvent. In a lithium primary battery including a non-aqueous electrolyte solution and a separator, the positive electrode contains a mixture of manganese dioxide and a lithium compound in an amount of 150 to 4
A surface-modified manganese dioxide containing 1 to 15 atom% of lithium based on the total amount of lithium and manganese, which is obtained by firing at 00 ° C, is used as an active material, and the solvent is ethylene carbonate, propylene carbonate, butylene carbonate, 20 to 80% by volume of at least one carbonic acid ester selected from the group consisting of dimethyl carbonate, diethyl carbonate and ethylmethyl carbonate,
It is a mixed solvent with 80 to 20% by volume of 1,2-dimethoxyethane, and the solute is lithium trifluoromethanesulfonate or lithium hexafluorophosphate.

As the manganese dioxide, either electrolytic manganese dioxide or chemical manganese dioxide can be used. However, since chemical manganese dioxide contains a large amount of impurities due to the manufacturing method, and it is difficult to obtain high density manganese dioxide, electrolytic manganese dioxide can be obtained. Preference is given to using manganese.

Examples of the lithium compound include lithium hydroxide, lithium carbonate, lithium nitrate and lithium oxide.

The firing temperature of the mixture of manganese dioxide and a lithium compound is 150 to 400 ° C. 150 ° C
If it is less than less than enough water is not removed,
On the other hand, when the temperature exceeds 400 ° C., the crystal structure of manganese dioxide changes and deactivates, and in any case, it becomes difficult to obtain a lithium primary battery exhibiting good low-temperature discharge characteristics.

The lithium content of the surface-modified manganese dioxide in the present invention is 1 to 15 atom% based on the total amount of lithium and manganese. Lithium content is 1 atomic%
If it is less than the above, it is difficult to sufficiently modify the surface of manganese dioxide, so that the lithium content is 15 atomic%.
If it exceeds the above range, the amount of manganese dioxide as the positive electrode active material decreases, and in any case, it becomes difficult to obtain a lithium primary battery exhibiting good low temperature discharge characteristics.

The non-aqueous electrolyte in the present invention contains 20 to 80% by volume of at least one carbonic acid ester selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.
It is obtained by dissolving lithium trifluoromethanesulfonate or lithium hexafluorophosphate in a mixed solvent containing 80 to 20% by volume of 1,2-dimethoxyethane. The solvent and solute of the non-aqueous electrolytic solution are limited in this way, even if the above-mentioned surface-modified manganese dioxide is used as the positive electrode active material, if another solvent or solute is used, a good low temperature is obtained. This is because it is not always possible to obtain a lithium primary battery that exhibits discharge characteristics.

[0011]

In the battery of the present invention, the surface-modified manganese dioxide is used as the positive electrode active material, and the non-aqueous electrolyte having excellent wettability with the surface-modified manganese dioxide is used as the non-aqueous electrolyte. As compared with the conventional lithium primary battery, the effective reaction area of the positive electrode during charging / discharging is large, and the low temperature discharge characteristics are excellent. The reason why the surface modification of manganese dioxide improves the wettability to a specific non-aqueous electrolyte is not clear even by the present inventors,
It is considered that lithium is generated and adhered to the surface of the manganese dioxide particles by the surface modification, and this lithium contributes to the improvement of the wettability of the manganese dioxide with respect to the specific non-aqueous electrolyte.

[0012]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited by the following examples, and various modifications can be made without departing from the scope of the invention. Is possible.

[Production of Positive Electrode] Manganese dioxide powder (particle size: 100 μm or less) as a positive electrode active material, and Table 1 or Table 2.
Various lithium compounds shown inside (particle size 100 μm or less)
And the atomic ratio of manganese to lithium is 90: 1.
Mix in a ratio of 0 and fire at 375 ° C for 2 hours,
A surface modified manganese dioxide powder was prepared.

[0014]

[Table 1]

[0015]

[Table 2]

Next, the surface-modified manganese dioxide powder or the manganese dioxide powder which has not been surface-modified, carbon (artificial graphite) as a conductive agent, and a binder are mixed at a weight ratio of 80:10:10. A disk-shaped positive electrode was produced by mixing and molding.

[Production of Negative Electrode] A lithium metal plate was punched out to produce a disk-shaped negative electrode.

[Preparation of Non-Aqueous Electrolyte] Various non-aqueous electrolytes were prepared using the mixed solvent and solute shown in Table 1 or Table 2. All solute concentrations were 1 mol / liter. For the binary solvent mixture, the volume ratio of the carbonic acid ester and 1,2-dimethoxyethane was all 1: 1. Also,
Regarding the ternary mixed solvent, the mixing ratio (volume%) of the two types of carbonic acid ester and 1,2-dimethoxyethane was all set to 30:30:40.

The abbreviations in Tables 1 and 2 indicate the following solvents, respectively. EC: ethylene carbonate DME: 1,2-dimethoxyethane PC: propylene carbonate BC: 1,2-butylene carbonate DMC: dimethyl carbonate EMC: ethyl methyl carbonate DEC: diethyl carbonate γ-BL: γ-butyrolactone SL: sulfolane THF: tetrahydrofuran DOS: 1,3-dioxolane

[Assembly of Lithium Primary Battery] The above positive electrode,
A flat type lithium primary battery (diameter 20 mm, height 2.5 mm) was assembled using the negative electrode and the non-aqueous electrolyte.
Of these, the batteries of the present invention are represented by A1 to A14, and the comparative batteries are represented by B1 to B15. A polyamide nonwoven fabric was used as the separator.

[Discharge capacity] At -20 ° C, each battery was charged to 5
The discharge capacity at a low temperature of each battery was obtained by discharging with a constant resistance discharge of kΩ at a final voltage of 2V. The results are shown in Tables 1 and 2 above.

From Tables 1 and 2, the batteries A1 to A1 of the present invention are shown.
It can be seen that No. 4 has a larger discharge capacity at −20 ° C. and is excellent in low temperature discharge characteristics as compared with Comparative Batteries B1 to B15.

[Relationship between Lithium Content of Surface Modified Manganese Dioxide and Low Temperature Discharge Characteristics] Ethylene carbonate and 1,
A non-aqueous electrolytic solution prepared by dissolving 1 mol / liter of lithium trifluoromethanesulfonate in a mixed solvent of 2-butylene carbonate and 1,2-dimethoxyethane in a volume ratio of 30:30:40 is used, and the mixture of manganese and lithium is used. The lithium content based on the total amount is 0.5 atom%, 1 atom%, 2
A lithium primary battery was assembled in the same manner as above, except that at least 5 atomic%, 8 atomic%, 15 atomic% or 20 atomic% of the surface-modified manganese dioxide was used as the positive electrode active material.

Next, each of these batteries was discharged under the same conditions as above, and the discharge capacity at -20 ° C of each battery was determined. The results are shown in Fig. 1. In FIG. 1, the battery A11 of the invention is shown.
The discharge capacity (−105 mAh) at −20 ° C. is also shown.

FIG. 1 shows the relationship between the lithium content of the surface-modified manganese dioxide and the low temperature discharge characteristics, the vertical axis represents the discharge capacity (mAh) at −20 ° C., and the horizontal axis represents the lithium content (atomic%). ) Is a graph shown. From FIG. 1, in order to obtain a lithium primary battery having a large discharge capacity at low temperatures, the lithium content is 1 to 15 atom%, preferably 2 to 8
It can be seen that it is necessary to use atomic percent surface modified manganese dioxide.

[Relationship between firing temperature of surface-modified manganese dioxide and low-temperature discharge characteristics] Mixing ratio (volume%) of ethylene carbonate, 1,2-butylene carbonate and 1,2-dimethoxyethane of 30:30:40 Using a non-aqueous electrolyte in which 1 mol / liter of lithium trifluoromethanesulfonate is dissolved in a solvent, and at 100 ° C and 150 °
C, 200 ° C, 300 ° C, 400 ° C or 450 °
Except that a surface-modified manganese dioxide having a lithium content of 10 atomic% based on the total amount of manganese and lithium obtained by firing a mixture of manganese dioxide and lithium hydroxide at C was used as the positive electrode active material. A lithium primary battery was assembled in the same manner as in.

Next, each of these batteries was discharged under the same conditions as above, and the discharge capacity at -20 ° C of each battery was determined. The results are shown in Figure 2. In FIG. 2, the battery A11 of the invention is shown.
The discharge capacity (−105 mAh) at −20 ° C. is also shown.

FIG. 2 shows the relationship between the firing temperature and the low-temperature discharge characteristics in the production of surface-modified manganese dioxide, the vertical axis represents the discharge capacity (mAh) at −20 ° C., and the horizontal axis represents the firing temperature (° C). )
It is the graph which took and showed. From FIG. 2, in order to obtain a lithium primary battery having a large discharge capacity at low temperature,
It can be seen that it is necessary to use the surface modified manganese dioxide obtained by firing at ~ 400 ° C.

[Relationship between mixing ratio of carbonic acid ester and 1,2-dimethoxyethane and low-temperature discharge characteristics] Volume ratio of ethylene carbonate and 1,2-dimethoxyethane 90: 1
0, 80:20, 50:50, 20:80 or 10: 9
Manganese and lithium obtained by firing a mixture of manganese dioxide and lithium hydroxide at 375 ° C. using a non-aqueous electrolyte in which 1 mol / liter of lithium trifluoromethanesulfonate was dissolved in a mixed solvent of 0. A lithium primary battery was assembled in the same manner as above except that surface-modified manganese dioxide having a lithium content of 10 atomic% based on the total amount of was used as the positive electrode active material.

Next, each of these batteries was discharged under the same conditions as above, and the discharge capacity at -20 ° C of each battery was determined. The results are shown in Fig. 3.

FIG. 3 shows ethylene carbonate and 1,2-
The relationship between the mixing ratio with dimethoxyethane and the low temperature discharge characteristics
3 is a graph showing the discharge capacity (mAh) at −20 ° C. on the vertical axis and the mixing ratio of ethylene carbonate and 1,2-dimethoxyethane on the horizontal axis. From FIG. 3, in order to obtain a lithium primary battery having a large discharge capacity at low temperature and excellent in low temperature discharge characteristics, ethylene carbonate and 1,2
-The mixing ratio with dimethoxyethane is 20:80 to 80: 2.
It can be seen that the range needs to be 0. It was confirmed that lithium carbonate primary batteries having excellent low-temperature discharge characteristics were obtained with other carbonic acid esters within the same mixing ratio range.

In the above embodiment, the case where the present invention is applied to the flat type lithium primary battery has been described. However, the shape of the battery is not particularly limited, and the present invention is applicable to a cylindrical type, a square type, etc.
It can be applied to lithium primary batteries of various shapes.

[0033]

Since the battery of the present invention has good wettability of the positive electrode with respect to the non-aqueous electrolyte, the positive electrode has a large effective reaction area and excellent low-temperature discharge characteristics.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the lithium content of surface-modified manganese dioxide and low-temperature discharge characteristics.

FIG. 2 is a graph showing the relationship between the firing temperature and the low-temperature discharge characteristics when producing surface-modified manganese dioxide.

[Figure 3] Ethylene carbonate (carbonic acid ester) and 1,
3 is a graph showing the relationship between the mixing ratio with 2-dimethoxyethane and low temperature discharge characteristics.

Front page continuation (72) Inventor Koji Nishio 2-5-5 Keihan Hon-dori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Toshihiko Saito 2-5-5 Keihan-hondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd.

Claims (3)

[Claims] 1. A lithium primary battery comprising a positive electrode, a negative electrode using metallic lithium or a lithium alloy as an active material, a non-aqueous electrolytic solution containing a solute and a solvent, and a separator,
The positive electrode is a material obtained by firing a mixture of manganese dioxide and a lithium compound at 150 to 400 ° C. and containing surface-modified manganese dioxide containing 1 to 15 atom% of lithium based on the total amount of lithium and manganese as an active material. And the solvent is ethylene carbonate, propylene carbonate,
20-8 at least one carbonic acid ester selected from the group consisting of butylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate
A lithium primary battery, which is a mixed solvent of 0% by volume and 80 to 20% by volume of 1,2-dimethoxyethane, and wherein the solute is lithium trifluoromethanesulfonate or lithium hexafluorophosphate. 2. The lithium compound is lithium hydroxide,
The lithium primary battery according to claim 1, which is lithium carbonate, lithium nitrate or lithium oxide. 3. The surface-modified manganese dioxide contains 2 to 8 atomic% lithium based on the total amount of lithium and manganese.
The lithium primary battery according to claim 1, which contains the lithium primary battery.