JPH03230475A - Lithium battery - Google Patents

Abstract

PURPOSE:To form a small-sized and thin Li battery maintaining high voltage for a long period by forming the Li battery constituted of a positive electrode mainly made of (C2H3N2)2 synthesized with quinoxaline which is a starting material and a negative electrode made of metal Li. CONSTITUTION:Quinoxaline 1.0g and lithium borate tetrafluoride l.9 g are solved in propylene carbonate 20ml, a metal body pressed with Li and Ni is immersed in this solution, for example, a container is sealed and left under this condition for ten days, a solid object thus generates is washed with water and heated and dried to obtain the synthetic powder (C2H3N2)2 0.8g. The (C2H3N2)2 powder is kneaded with acetylene black and polytetra fluoroethylene at the preset ratio, a kneaded object is enveloped by titanium steel and molded to obtain a positive electrode. Metal Li is used for a negative electrode, sodium borate tetrafluoride is solved as an electrolyte in propylene carbonate at the preset concentration for an electrolytic liquid to form a Li battery.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a lithium secondary battery with high energy density and stable performance.

[Conventional technology]

A lithium battery using metallic lithium for fri can obtain an electromotive force of nearly 3 cm, and since lithium itself is a light metal, it can provide lightweight performance with high energy density. Utilizing these characteristics, it has already been put into practical use as small and thin batteries such as cylindrical, button, and coin shapes.

Various types of active materials are used for the positive electrode of lithium batteries, but the most typical system uses graphite fluoride ((CF), ), which is an interlayer compound of fluorine and graphite, as the positive electrode active material. This is a fluorinated graphite-lithium battery.

This type of battery is, for example, lithium tetrafluoroborate (i, 11
1Fa), an aprotic electrolyte such as lithium hexafluoroarsenate (LiAsFb). Discharge is performed using an electrolytic solution dissolved in a TJ medium through the reaction of the following formula.

(CF) 10nLi-C, 10nLi In fluorine compounds other than fluorinated graphite, the reaction with lithium does not proceed smoothly because the fluorine atoms are strongly bonded, and the discharge performance as a battery is not satisfied. do not.

[Problem to be solved by the invention]

The inventors developed an m-horizontal lithium battery that uses fluorine atoms in an inorganic fluorine compound used as an electrolyte as a positive electrode active material.
We have already developed a product in which a lithium salt containing a fluorine atom is contained in an electrolytic solution solvent or a positive electrode material, and a nitrogen-containing aromatic compound is dissolved in the electrolytic solution (Patent Application No. 1983-
No. 313303, patent application No. 1-182276).

In this composition system, a battery using phthalazine as a nitrogen-containing aromatic compound has a high pressure discharge property of about 2.6 V, but has a problem of a small discharge capacity. Therefore, when used as a practical battery, it is essential to improve the utilization rate of the positive electrode active material.

The present invention was obtained as a result of research aimed at improving the utilization of active materials by focusing on the high-pressure discharge performance of quinoxaline. The aim is to provide lithium batteries with high density and stable performance.

[Means for Solving the Problems] A lithium battery according to the present invention for achieving the above object includes a positive electrode mainly composed of (Cm Hs Nz) synthesized using quinoxaline (CB) (16NZ) as a starting material; Its structural feature is that it consists of a metal lithium (Li) negative electrode.

The (C, Hs Nz)z substance, which is the main component of the positive electrode material, is synthesized using quinoxaline as a starting material in the following steps.

Quinoxaline (CsH, N,
) from 30 to 100 g/l and lithium tetrafluoroborate (
Electrolyte) is dissolved in each concentration range from 0.5 to 1.5 mol/l, and a metal body with two different metals, such as lithium (Li) and nickel (Ni), is pressed into the prepared solution. Soak. If you leave it in this state for 1 to 2 weeks,
A powder having a molecular structure of (Cs H5Nz)x is produced. The produced powder is washed with water or an appropriate organic solvent and then dried.

The positive electrode of the lithium battery according to the present invention contains at least 60% by weight of (c, Hs Nz) synthesized in the above process as a main component, and carbonate, graphite powder, carbon powder as a conductive material. , a carbonaceous material such as coke powder, and a resin binder such as polytetrafluoroethylene (PTPE) are mixed and molded. The blending amount of the carbonaceous material that becomes the conductive material is (Cs Hs Nz)
It is desirable to set the Z component in the range of 0 to 50 parts by weight. If it is less than 10 parts by weight, the conductivity as a positive electrode will be insufficient, and if it exceeds 50 parts by weight, the energy density per unit weight will decrease. descend. Further, the blending amount of the resin binder is preferably in the range of 1 to 10 parts by weight per 100 parts by weight of the main component. This is because if the amount is less than 1 part by weight, molding becomes difficult, and if the amount exceeds 10 parts by weight, the energy density per unit weight will decrease.

Metal lithium (Li) is used for the negative electrode.

For example, lithium tetrafluoroborate (LiBF) is used as the electrolyte.
Inorganic lithium fluoride salts such as lithium hexafluorophosphate (LiPFh) and lithium hexafluoroarsenate (LiAsF) are used, but lithium tetrafluoroborate or lithium hexafluoroarsenate is preferable from the viewpoint of battery characteristics. be. These electrolytes are dissolved in an aprotic organic solvent such as propylene carbonate, T-butyrolactone, or tetrahydrofuran to form an electrolytic solution.

[For production]

In the lithium battery of the present invention having the above configuration, the (Cm Hs Nz) component, which is the main component of the positive electrode, acts as an active material intermediate to promote an electrochemical reduction reaction that liberates fluorine atoms from the electrolyte material, Improves discharge function by generating lithium fluoride.

In addition, in phthalazine or its derivatives, N atoms are present at the 2nd and 3rd positions in the molecule, so these two N atoms
Complexes in which each atom is coordinated with an electron acceptor such as B F s are difficult to form due to steric hindrance. On the other hand, in quinoxaline or its derivatives, steric hindrance is suppressed because N atoms are present at the 1st and 4th positions, and it is thought that a complex is formed by coordination of electron acceptors to these two N atoms. It will be done. In other words, since quinoxaline or its derivatives can form complexes with more electron acceptors, the discharge characteristics can be improved.

Furthermore, since the powder of (CIl H5N2)Z is insoluble in the electrolyte, there is no deterioration in performance even if it is stored for a long period of time. Therefore, the discharge capacity is significantly improved compared to the embodiment in which quinoxaline is dissolved in the electrolytic solution.

Through such effects, high energy density performance with good storage stability is exhibited.

〔Example〕

Hereinafter, the present invention will be explained based on examples.

Example 1 (1) Synthesis of (C,H3Nz)z Quinoxaline (C8H6N2) 1. Og and 1.9g of lithium tetrafluoroborate (1,1BFa) to 120m of propylene carbonate? I solved 8. A metal body having lithium (Li) and nickel (Ni) bonded together was immersed in this solution, the container was sealed, and the container was left in this state for 10 days. Then, after collecting the generated solid matter and washing it thoroughly with water,
Dry at a temperature of 00°C.

It was confirmed that the obtained powder had a molecular structure of (Cs Hs Nz)z, and the synthesized amount was 0.8 g.

(2) Composition of Lithium Battery 100 inches of the (Ce H5N2) 2 powder described in Section 2 was kneaded with 30 mg of acetylene black and 2 mg of polytetrafluoroethylene (PTFE), and the kneaded product was wrapped in a titanium mesh and molded to form a positive electrode. . The negative electrode is metallic lithium (L
i). The electrolytic solution contains 1 mo of lithium tetrafluoroborate (LiBF4) as an electrolyte in propylene carbonate.
l//! A solution dissolved at a concentration of 1.5 raQ was used.

(3) Performance evaluation The lithium battery configured as described above was discharged at a constant current of 0.3 mA. The discharge voltage in this case is 2.8-1.9
V, and the discharge capacity was 92.3+nA Hr.

In addition, the discharge curve is shown in the figure. The illustrated discharge curve shows that the lithium battery of this example has the ability to maintain high voltage for a long time.

Example 2 The same lithium battery as in Example 1 was discharged at a constant current of Is^. The discharge voltage according to this example is 2.6-1.9 V
, the discharge capacity was 63.7 mA Hr.

The discharge curve is also included in the figure. These results show that although the voltage level decreased slightly due to the increase in discharge current, it was approximately 2.
It was observed that the voltage could be maintained at a voltage lower than V.

Example 3 When the lithium battery of Example 1 was discharged at a constant current of l-pass for a period of one month after manufacture, the discharge voltage was 2.
6-1.9 V, and the discharge capacity was 64.8 mA Hr. The discharge curve in this case is also shown in the figure. The discharge curve was exactly on the discharge curve of Example 2, and it was found that the product had excellent storage stability without deterioration in performance even after being left for a long time.

Example 4 The battery configuration was the same as in Example 1 except that the electrolyte was replaced with lithium hexafluoroarsenate (LiAsFa), and the battery was discharged at a constant current of 1 mA. The discharge voltage according to this example is 2.3
~1.9 V, and the discharge capacity was 56.3 mA Hr. The discharge curve is also included in the figure. Although the discharge curve showed a slight tendency to decrease compared to Example 2, it had stable performance as a whole.

Comparative Example As a positive electrode, 30 mg of acetylene black was kneaded with 2 tags of polytetrafluoroethylene (PTFE), then wrapped in a titanium mesh and molded.
The composition was prepared by dissolving mg. A lithium battery was produced under the same conditions as in Example except for the following. This battery is 1
When discharged at a constant voltage of mA, the discharge voltage was 2.7
~2.3 V, the discharge capacity was 14.3 mA Hr.

In addition, the discharge curve is also shown in the figure, and in this example, although the voltage was high, the discharge behavior showed an extremely small discharge capacity.

〔Effect of the invention〕

As described above, according to the present invention, by using CCe H5Ng)2 synthesized from quinoxaline as the main component of the positive electrode, it has a high energy density over a long period of time and has good storage stability without deterioration of performance over time. It is possible to provide a high-performance lithium battery with Therefore, small size,
It is expected to be useful as a thin battery.

[Brief explanation of drawings]

The figure shows discharge curves of lithium batteries according to Examples and Comparative Examples.

Claims (1)

[Claims] 1. A lithium battery comprising a positive electrode mainly composed of (C_8H_5N_2)_2 synthesized using quinoxaline (C_8H_6N_2) as a starting material, and a negative electrode of metallic lithium (Li). 2. The lithium battery according to claim 1, wherein the electrolyte is a composition prepared by dissolving lithium 2,4 fluoroborate (LiBF_4) or lithium hexafluoroborate (LiAsF_6) in an aprotic solvent.