JP3434557B2 - Non-aqueous solvent secondary battery - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium-based metal comprising a vanadium pentoxide for a positive electrode and lithium or an alkali metal alloy containing lithium as a main component (hereinafter, referred to as a negative electrode). And a non-aqueous solvent secondary battery containing a carbonaceous material as a support for the lithium-based metal. 2. Description of the Related Art In recent years, with the development of electronic equipment, there has been a demand for the development of a secondary battery which is small and lightweight, has a high energy density, and can be repeatedly charged and discharged. As a secondary battery of this type, metal lithium or a lithium alloy was used as a negative electrode active material, and an oxide such as molybdenum, vanadium, titanium, or niobium, a sulfide thereof, or a selenium compound thereof was used as a positive electrode active material. Things are known. However, a battery system using metallic lithium or a lithium alloy as the negative electrode active material has a drawback that the charge / discharge cycle life is short because repetition of charge / discharge generates dendrite on the negative electrode. In order to solve this problem, a solution has been achieved by using lithium and a carbonaceous material as a carrier for the negative electrode. In particular, a non-aqueous solvent secondary battery using a vanadium pentoxide for the positive electrode, a lithium-based metal for the negative electrode, and a carbonaceous material as a carrier for the lithium-based metal has a high operating voltage and significantly improves the charge / discharge cycle life. Is attracting attention as a possible battery. However, a nonaqueous solvent secondary battery using a lithium-based metal for the negative electrode and a carbonaceous material as the lithium-based metal carrier has a discharge capacity that is lower than that of a secondary battery using metallic lithium or a lithium alloy as the negative electrode as it is. And its improvement remains a major challenge. An object of the present invention is to solve the above problems and to provide a high capacity non-aqueous solvent secondary battery. SUMMARY OF THE INVENTION The present invention relates to a lithium-based metal comprising vanadium pentoxide in a positive electrode and lithium or an alkali metal alloy containing lithium as a main component in a negative electrode, and a carrier of the lithium-based metal. The present invention relates to a non-aqueous solvent secondary battery containing a carbonaceous material, wherein the average particle size of the secondary particles of vanadium pentoxide of the positive electrode is 30 to 80 μm. [0007] Vanadium pentoxide generally has a number of very fine primary particles aggregated and bound to form secondary particles. The present inventors have paid attention to the particle size of the secondary particles, and have found that there is the following correlation between the particle size of the secondary particles and the discharge capacity of the battery. That is, when the particle size of the secondary particles increases, the specific surface area decreases, and as a result, the contact area between the positive electrode active material, vanadium pentoxide, and the electrolyte decreases, and the utilization rate of the positive electrode active material decreases. By that, the battery capacity also decreases, and the maximum particle size of the secondary particles that can avoid such a decrease in the utilization rate of the positive electrode active material,
150 μm. In the present invention, the average particle size of the secondary particles of vanadium pentoxide is 150 μm or less, preferably 3 μm or less.
0 to 80 μm, more preferably 50 to 80 μm
It is. When the average particle size of the secondary particles exceeds 150 μm,
Since the contact area between the particles and the electrolyte decreases, the utilization rate of vanadium pentoxide decreases, and the battery capacity cannot be increased.
When the particle size is too small, the diffusibility of lithium ions decreases and the electrical resistance of the positive electrode mixture increases. Therefore, the particle size of the secondary particles is preferably 30 to 80 μm. Further, the vanadium pentoxide secondary particles having the above-mentioned particle diameter can be obtained by sieving vanadium pentoxide particles as a raw material. For sieving, a vibration sieving device such as a resonance type or a circular vibration type, or an in-plane motion sieving device such as a reciprocating type can be used. [0010] The particle size of the secondary particles of vanadium pentoxide is measured by a laser diffraction method using dry air as a dispersion medium. The positive electrode used in the present invention comprises the above-mentioned vanadium pentoxide as an active material, carbon black such as acetylene black, a conductive material such as nickel powder, polyethylene, polypropylene, polytetrafluoroethylene, polyacrylic acid, and the like. It has a composition containing a binder such as polyacrylate. The lithium carrier used in the negative electrode of the present invention includes a carbonaceous material obtained by firing an organic polymer compound such as phenol resin, polyacrylonitrile, and cellulose; and a carbonaceous material obtained by firing coke and pitch. Materials; and carbonaceous materials such as artificial graphite and natural graphite. The production of the negative electrode is performed as follows. For example, a carbonaceous material obtained by calcining the polymer compound in an atmosphere of an inert gas such as argon or nitrogen at a temperature of 500 to 3,000 ° C., preferably 800 to 1,500 ° C. and at normal pressure or reduced pressure. Then, the same binder as that used for the positive electrode is added and mixed to form a desired shape such as a pellet. Next, a lithium-based metal is added to the molded body to form a negative electrode. As a method for incorporating the lithium-based metal into the compact such as a pellet, a vapor deposition method, a chemical impregnation method, an electrolytic impregnation method, or the like can be adopted. The alkali metal alloy contains at least 90% by weight of lithium, preferably 91 to 93% by weight. As the separator, a non-woven fabric or a porous film of a polyolefin resin such as polyethylene or polypropylene can be used. As the electrolyte, for example, one or more nonaqueous organic solvents selected from propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, γ-butyrolactone, 2-methyltetrahydrofuran and the like are mixed with LiC
electrolytes such as 10 ₄ , LiPF ₆ , LiBF ₄
A solution dissolved at a concentration of 1.5 mol / l, preferably 0.5 to 1.0 mol / l can be used. The non-aqueous solvent secondary battery of the present invention comprises the above positive electrode,
It is obtained by assembling a battery element including a negative electrode and a separator impregnated with an electrolyte. According to the present invention, the electric resistance of the positive electrode mixture is reduced and the diffusivity of lithium ions is improved, whereby a high capacity non-aqueous solvent secondary battery can be provided. . Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. Example 1 (1) Preparation of Positive Electrode Using a standard sieve of 325, 280, 250, 170, 120, or 80 mesh, the secondary particles of vanadium pentoxide were converted to an average particle diameter of 10 μm (sample A) and 30 μm (sample A). Sample B), 50 μm (Sample C), 80 μm (Sample D), 100
6 μm (sample E) and 150 μm (sample F) were separated by sieving. The average particle size was measured using PRO-70 manufactured by Seishin Enterprise Co.
It was measured using 00S. Each of the above samples was used as an active material, carbon black was used as a conductive material, and polytetrafluoroethylene was used as a binder. The weight ratio of the active material, the conductive material, and the binder was 90: 6: 4. After mixing, mixing and kneading, six types of positive electrodes were produced by press-forming at a pressure of 250 MPa (2.5 ton / cm ² ) into pellets having a diameter of 15 mm and a thickness of 0.77 mm. (2) Preparation of negative electrode The phenol resin powder was calcined in air at 1,000 ° C. for 3 hours to obtain a carbonaceous powder. This powder was mixed with a methacrylic acid alkyl ester-butadiene copolymer in a weight ratio of 93: 7 as a binder, mixed and kneaded, and then mixed at 250 MPa.
a At a pressure of (2.5 ton / cm ² ), it was pressed into a pellet having a diameter of 15.7 mm and a thickness of 0.90 mm. Next, lithium was contained in the pellet formed body by an electrolytic impregnation method to form a negative electrode. (3) Battery Assembly FIG. 1 is a sectional view of a non-aqueous solvent secondary battery according to the present invention. The non-aqueous solvent secondary battery was assembled as follows. First, the positive electrode (2) was housed inside a positive electrode container (1) made of stainless steel via a positive electrode current collector (3) made of stainless expanded metal having a diameter of 12 mm and a thickness of 0.05 mm. Next, a separator (4) in which an electrolyte solution obtained by dissolving lithium perchlorate in propylene carbonate to a concentration of 0.7 mol / l was impregnated in a propylene nonwoven fabric was placed on the positive electrode (2). Further, the inner surface of the negative electrode container (5) made of stainless steel has a diameter of 12 m.
A negative electrode (7) was mounted via a negative electrode current collector (6) made of nickel expanded metal having a thickness of 0.10 mm and a thickness of 0.10 mm. Finally, the negative electrode container (5) is fitted into the opening of the positive electrode container (1) via an insulating gasket (8),
The positive electrode container (1) is caulked and the positive electrode container (2), the separator (4) and the negative electrode (7) are sealed in the positive electrode container and the negative electrode container (5), so that the outer diameter is 20 mm and the thickness is 2.5 mm.
Twenty mm coin-shaped non-aqueous solvent secondary batteries were assembled for each of the positive electrodes A to F. (4) Charge / discharge test The battery assembled as described above was charged at a constant current of 1 mA until it reached 3.4 V, and then discharged at a constant current of 1 mA to 1.8 V. The discharge capacity was calculated from the discharge time. Table 1 shows the results. The discharge capacity value is an average value of 10 batteries. Comparative Example 1 A battery similar to that of Example 1 was assembled except that secondary particles of vanadium pentoxide having an average particle diameter of 300 μm (sample G) were used as a positive electrode active material, and a similar charge / discharge test was performed. . Table 1 shows the results. [Table 1] As is clear from Table 1, a high capacity nonaqueous solvent secondary battery can be obtained by using vanadium pentoxide secondary particles having an average particle size of 150 μm or less as the positive electrode active material.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a coin-shaped non-aqueous solvent secondary battery of the present invention. [Description of Symbols] 1 ... Positive electrode container 2 ... Positive electrode 3 ... Positive electrode current collector 4 ... Separator 5 ... Negative electrode container 6 ... Negative electrode current collector 7 ... Negative electrode 8 ... Gasket

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-230668 (JP, A) JP-A-4-280068 (JP, A) JP-A-6-168714 (JP, A) 285363 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 4/00-4/62

Claims (1)

(57) [Claims 1] A lithium-based metal comprising vanadium pentoxide in a positive electrode and lithium or an alkali metal alloy containing lithium as a main component in a negative electrode, and carbon as a carrier of the lithium-based metal. In a non-aqueous solvent secondary battery containing a porous material, the average particle diameter of the secondary particles of vanadium pentoxide of the positive electrode is 3
A non-aqueous solvent secondary battery having a thickness of 0 to 80 μm.