JP3325967B2 - Non-aqueous solvent secondary battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a non-aqueous solvent secondary battery, and more particularly to a non-aqueous solvent secondary battery having an improved positive electrode active material.

[0002]

2. Description of the Related Art In recent years, non-aqueous solvent batteries using light metals such as lithium, sodium, and aluminum as negative electrode active materials have attracted attention as high energy density batteries, and manganese dioxide (MnO ₂ ), fluoride Carbon [(C
F) n], primary batteries using thionyl chloride (SOCl ₂ ) and the like are already widely used as power supplies for calculators, watches, and memories. Further, in recent years, with the miniaturization and weight reduction of various electronic devices such as VTRs and communication devices, demands for secondary batteries having a high energy density as a power source for such devices have increased, and non-aqueous solvent secondary batteries using a light metal as a negative electrode active material have been required. Battery research is being actively conducted.

[0003] By the way, non-aqueous solvent secondary batteries use a light metal such as lithium, sodium, or aluminum for the negative electrode,
Propylene carbonate (PC), 1,2-bimethoxyethane (DME), γ-butyrolactone (γ-BL),
L in a non-aqueous solvent such as tetrahydrofuran (THF)
A material in which an electrolyte such as iClO ₄ , LiBF ₄ , LiAsF ₆ , LiPF ₆ is dissolved is used, and a material using mainly TiS ₂ , MoS ₂ , V ₂ O ₅ , V ₆ O ₁₃ or the like as a positive electrode active material has been studied. I have.

On the other hand, MnO ₂ used in a non-aqueous solvent primary battery has the advantage of being low in cost, so that
_Although it has been considered to use ₂ as a positive electrode active material of a secondary battery, it is known that LiMn ₂ O ₄ having a spinel structure has reversibility of charge and discharge, and a secondary battery using this is also known. Has been studied. [Mat. Res. Bull
l. , Vol. 18, pp 461-472 (1983)
reference〕

[0005]

Incidentally, in the above-described nonaqueous solvent secondary battery using spinel type LiMn ₂ O ₄ as a positive electrode active material, the positive electrode undergoes volume expansion or contraction at the time of charging and discharging. In addition, the active material particles fall off from the positive electrode, which becomes more prominent as the depth of discharge becomes deeper or the discharge becomes heavier, and the charge / discharge cycle characteristics are not always sufficient.
In addition, since the active material or the conductive material is a fine powder, a large amount of a binder is required to sufficiently bind the active material or the conductive material to the metal core provided with the conductive layer. For this reason, there have been problems in terms of the internal resistance of the battery and the economy.

The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide an economical non-aqueous solvent secondary battery having excellent charge / discharge characteristics and high current discharge characteristics. is there.

[0007]

In order to achieve the above object, the present invention provides a negative electrode comprising a light metal and a spinel type Li.
In a non-aqueous solvent secondary battery including a positive electrode made of a positive electrode active material mainly composed of Mn ₂ O ₄ and an electrolytic solution in which an electrolyte is dissolved in a non-aqueous solvent, an aromatic material having a benzene ring in the positive electrode active material It is characterized in that a material to which a hydrocarbon is added is used as a positive electrode active material.

The spinel type LiMn ₂ O ₄ added with an aromatic hydrocarbon having a benzene ring used as the positive electrode active material of the non-aqueous solvent secondary battery of the present invention is LiMn ₂ O ₄
The powder can be obtained by immersing the powder as it is or in the form of pellets or sheets in the aromatic hydrocarbon, more preferably by subjecting the powder to a reduced pressure treatment, and then air-drying.

The above aromatic hydrocarbon having a benzene ring includes benzene, toluene, xylene, ethylbenzene, diethylbenzene, isopropylbenzene, amylbenzene, diamylbenzene, triamylbenzene, tetraamylbenzene, dodecylbenzene, didecylbenzene, Dodecylbenzene, amyltoluene, p-cymene and the like.

[0010]

According to the present invention, by adding an aromatic hydrocarbon having a benzene ring to spinel-type LiMn ₂ O ₄ as a positive electrode active material, these are selectively added to active points of a LiMn ₂ O ₄ spinel structure. It adsorbs and stabilizes this part to prevent collapse, and facilitates diffusion of lithium ions during charge and discharge. In addition, when mixed with a conductive material or a binder, they tend to adhere evenly, and the mixing ratio per unit area of the electrode is arranged at a constant ratio. It is possible to make it difficult for the material powder to peel or fall off. Therefore, it is possible to obtain a non-aqueous solvent battery excellent in large current discharge characteristics and reversibility of charge and discharge.

[0011]

Embodiments of the present invention will be described below in detail. Embodiment 1 FIG. 1 is a longitudinal sectional view of a cylindrical non-aqueous solvent secondary battery according to one embodiment of the present invention. As shown in the figure, a non-woven polypropylene fabric impregnated with a negative electrode 6 made of a metallic lithium foil and an electrolytic solution obtained by dissolving 1 mol / l of LiPF ₆ in a solvent obtained by mixing propylene carbonate and 2-methyltetrahydrofuran at a ratio of 1: 1. A separator 5 and a positive electrode 4 manufactured by a method described later are laminated in this order to form a band, and an electrode group (power generation element) 3 in which the band is spirally wound also serves as the negative electrode terminal 2. On the electrode group 3 housed in the bottom cylindrical container 1, an insulating paper 7 having a central opening is placed. In addition, an insulating sealing plate 8 is provided in the upper opening of the bottomed cylindrical container 1 in a liquid-tight manner by caulking the container 1 or the like, and a positive electrode terminal 9 is provided at the center of the insulating sealing plate 8. Mated. This positive electrode terminal 9 is connected to the positive electrode 4 of the electrode group 3 via a positive electrode lead 10. In addition, the negative electrode 6 of the electrode group 3 is connected to the container 1 which is a negative electrode terminal via a negative electrode lead (not shown).

The container 1 contains an electrolyte solution of 2-methyltetrahydrofuran in which 1.5 mol of lithium hexafluoride arsenate (LiAsF ₆ ) is dissolved.

The positive electrode 4 was manufactured by the following method. First, a spinel type LiMn ₂ O ₄ powder obtained by heating a mixture of manganese dioxide (MnO ₂ ) and lithium carbonate at a predetermined ratio at 800 ° C. for 4 hours is one of the aromatic hydrocarbons. It is immersed in toluene, decompressed, and then air-dried. Spinel-type Li obtained
80% by weight of Mn ₂ O _{4 is} 15% by weight of acetylene black
And 5% by weight of polytetrafluoroethylene powder to form a sheet, which was then pressed against an expanded metal current collector to produce a strip-shaped positive electrode having a width of 40 mm and a length of 200 mm.

Example 2 The spinel-type LiMn ₂ O ₄ powder obtained by the same method as in Example 1 was immersed in o-xylene, one of aromatic hydrocarbons, and subjected to a reduced pressure treatment.
Thereafter, a battery was fabricated in the same manner as in Example 1 except that spinel-type LiMn ₂ O ₄ obtained by air-drying was used as a positive electrode active material.

Comparative Example Spinel-type LiMn ₂ O ₄ powder 80 obtained by the same method as in Example 1 or Example 2
A battery was produced in the same manner as in Example 1 or Example 2, except that the weight% was used without being immersed in an aromatic hydrocarbon having a benzene ring.

Next, the battery of this embodiment and the battery of the comparative example were discharged at a current density of 0.5 mA / cm ² to 3 to ² V, and then repeatedly charged to 3 V. When the capacity retention was measured from the capacity, the characteristic diagram shown in FIG. 2 was obtained. 2, A indicates the characteristic curve of the battery of Example 1, B indicates the characteristic curve of the battery of Example 2, and C indicates the characteristic curve of the battery of Comparative Example. As is clear from FIG. 2, the battery of the present example can maintain a high capacity even when repeatedly used and has excellent performance as compared with the battery of the comparative example.

In the above embodiment, toluene and o-xylene were exemplified. In addition, benzene, m-xylene, p-xylene, methylenebenzene and the like also showed an improvement in battery capacity and cycle life.

[0018]

As described above, according to the present invention,
A non-aqueous electrolyte secondary battery having excellent charge / discharge cycle characteristics and excellent high-current discharge characteristics can be provided.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view of a cylindrical nonaqueous solvent battery showing one embodiment of the present invention.

FIG. 2 is a characteristic diagram comparing the number of cycles versus the capacity retention ratio between the battery of the present invention and a battery of a comparative example.

[Explanation of symbols]

1: Stainless steel capacity, 2: Negative electrode terminal, 3: Electrode group, 4:
Positive electrode, 5 ... separator, 6 ... negative electrode, 7 ... insulating paper, 8 ... sealing plate, 9 ... positive electrode terminal.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroyoshi Nose 3-4-1-10 Minamishinagawa, Shinagawa-ku, Tokyo Inside Toshiba Battery Corporation (72) Inventor Takumi Uchida 3-4-1 Minamishinagawa, Shinagawa-ku, Tokyo No. Toshiba Battery Co., Ltd. (72) Norihito Kurisu, Inventor No. 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo Toshiba Battery Co., Ltd. (72) Inventor Tsuchiyama, etc. 3-4-1 Minamishinagawa, Shinagawa-ku, Tokyo No. Toshiba Battery Co., Ltd. (56) References JP-A-5-135760 (JP, A) JP-A-6-2311753 (JP, A) JP-A-6-325766 (JP, A) JP-A-6-325766 318459 (JP, A) JP-A-5-129019 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 4/02 H01M 4/58 H01M 4/62 H01M 10/40

Claims (1)

(57) [Claims] 1. A negative electrode comprising a light metal and a spinel type Li
In a non-aqueous solvent secondary battery including a positive electrode made of a positive electrode active material mainly composed of Mn ₂ O ₄ and an electrolytic solution in which an electrolyte is dissolved in a non-aqueous solvent, an aromatic material having a benzene ring in the positive electrode active material A non-aqueous solvent secondary battery using a hydrocarbon-added material as a positive electrode active material.