JPH0468747B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a secondary battery that is small in size and has a large charging capacity, and more particularly to a battery that uses lithium as a negative electrode active material. Many proposals have been made for high energy density batteries that use lithium as a negative electrode active material. For example, batteries that use graphite and fluorine intercalation compounds as positive electrode active materials and lithium metal as negative electrode active materials are known. (See US Pat. No. 3,514,337). In addition, lithium batteries using fluorinated graphite as a positive electrode active material (manufactured by Matsushita Electric) and lithium batteries using manganese dioxide as a positive electrode active material (manufactured by Sanyo Electric) are already on the market. However, these batteries have the disadvantage that they are not rechargeable and cannot be used as secondary batteries. In addition, titanium, zirconium,
Secondary batteries using sulfides, selenides, and tellurides of hafnium, niobium, tantalum, and vanadium (see US Pat. No. 4,089,052) and secondary batteries using chromium oxide, niobium selenide, etc. [J.Electrochem .Soc, Vol.124 No.7 No.968
Page and No. 325 (1977)], but these batteries could not necessarily be said to be sufficient due to their battery characteristics. Furthermore, a Li battery using metal phthalocyanine as a positive electrode active material is disclosed in US Pat. No. 4,251,607, but this patent does not include any description of the particle size of the positive electrode active material or the processing conditions for its raw materials. The present invention has been made in view of the current situation, and an object thereof is to provide a secondary battery that is small in size and has excellent charge/discharge characteristics. To summarize the present invention, the positive electrode active material of the battery of the present invention is crystalline ultrafine particles of a phthalocyanine-related compound with an average particle size of 1 μm or less formed by heating and evaporating a phthalocyanine raw material in a dilute inert gas atmosphere, and negative electrode active materials. It is characterized in that it is composed of lithium as a substance and a substance that is chemically stable with respect to the positive electrode active material and lithium as an electrolyte, and that allows lithium ions to move because of an electrochemical reaction with the positive electrode active material. According to the present invention, by using phthalocyanine-related compound ultrafine particles as a positive electrode active material, a secondary battery that is small and has good charge and discharge characteristics can be produced. The present invention will be explained in more detail. As described above, the secondary battery according to the present invention uses ultrafine particles of a phthalocyanine compound, that is, ultrafine particles of a metal or nonmetallic compound having a phthalocyanine nucleus, as the positive electrode active material. Such phthalocyanine compounds are not fundamentally limited in the present invention. For example, iron phthalocyanine, copper phthalocyanine, zinc phthalocyanine, manganese phthalocyanine, fluorochrome phthalocyanine, cobalt phthalocyanine, nickel phthalocyanine, gallium phthalocyanine chloride, vanadyl phthalocyanine, silver phthalocyanine, cadmium phthalocyanine, tin phthalocyanine dichloride, aluminum phthalocyanine chloride, aluminum phthalocyanine dichloride, magnesium Examples include one or more compounds selected from the group consisting of phthalocyanine, lithium phthalocyanine, metal-free phthalocyanine, and the like. The average particle size of such ultrafine phthalocyanine compound particles is preferably 1 μm or less. Using such ultrafine particles not only increases the reaction surface area and improves the acquired current, but also
The average battery reaction due to the smaller particle size, and the uniformity of the battery reaction due to the uniform particle size,
This is to significantly improve discharge voltage flattening. In order to produce the ultrafine particles of a fluorocyanine-sized compound as described above, an apparatus as shown in FIG. 1, for example, is used. That is, an ultrafine particle collection container 2 is provided in a vacuum chamber 1, an evaporation source 3 is placed on the bottom of the container 2, and the evaporation source 3 is connected to a power source 4 for the evaporation source. Furthermore, the vacuum chamber 1 is connected via a regulator 5 to an inert gas (for example He) pump 6.
In the figure, 7 is a window for observing the inside of the vacuum chamber 1, 8 is a manometer, and 9 is a piranha vacuum gauge. Inert gas is introduced into the vacuum chamber 1 from an inert gas cylinder 6 via the regulator 5 to create an inert gas diluted atmosphere inside the vacuum chamber 1, and the phthalocyanine raw material 3 (evaporation source) is heated by the power source 4 to evaporate it. let The evaporated raw material 3 collides with the inert gas, rapidly cools down, becomes supersaturated, and generates ultrafine particles. The concentration of inert gas at this time is preferably 10~
It is 100 torr. This is because if it exceeds 100 torr, the particle size of the particles becomes too large. In addition, if the amount is less than 10 torr, it becomes difficult to generate particles. Further, the temperature of evaporation is preferably 300 to 600°C. This is because if the temperature exceeds 600°C, the particle size becomes too large, and if the temperature is below 300°C, the raw material becomes difficult to evaporate. The ultrafine particles thus produced can have an average particle size of 1 μm or less without impairing their crystallinity. When the ultrafine particles of the phthalocyanine compound as the positive electrode active material in the present invention are used as a positive electrode, the positive electrode is prepared by forming a powder of these compounds or a mixture of the same and a binder powder into a film on a support such as nickel or copper. These compound powders are pressure-molded or fitted with carbon powder for imparting conductivity, and the mixture is placed in a metal container, or the mixture is mixed with a binder container to form a support such as nickel or copper. It is formed by means such as coating it on top, drying it, and forming it into a film shape. Lithium, which is the negative electrode active material, is formed in the form of a sheet, as in general lithium batteries, or by pressing the sheet onto a nickel or copper mesh to form the negative electrode. As the electrolyte, aprotic organic solvents such as propylene carbonate, ethylene carbonate, γ-butyrolactone, dimethyl sulfoxide, acetonitrile, formamide, dimethylformamide, nitrometh, etc. and LiClO ₄ , LiAlCl ₄ , LiBF ₄ ,
Known electrolytes generally used in batteries using lithium as a negative electrode active material can be used, such as a combination with a lithium salt such as LiCl, or a solid electrolyte or molten salt using Li ⁺ as a conductor. Furthermore, if necessary due to the battery structure, a diaphragm made of porous polypropylene or the like may be used. Next, examples of the present invention will be described, but the present invention is not limited to these in any way. In addition, in the examples, the production and measurement of batteries are
It was held in an Ar atmosphere. Example 1 FIG. 2 is a schematic cross-sectional view of a battery cell for measuring characteristics of a button-type battery, which is a specific example of the present invention.
Ni-plated brass container, 22 is a lithium negative electrode,
23 is a porous polypropylene diaphragm, 24 is a felt made of carbon fiber, 25 is a positive electrode mixture, 2
6 indicates a Teflon container, and 27 indicates a Ni lead wire. Positive electrode mixture 25 is placed in the concave chamber of container 21 (diameter 26 mm).
Insert the felt 24 for electrolyte impregnation on top of it.
A lithium negative electrode 22 was placed thereon with a diaphragm 23 in between, and the container 26 made of Teflon was sealed. The lithium negative electrode 22 is a disk with a diameter of 20 mm, and the felt 2
4 and the diaphragm 23 were also disc-shaped. As the electrolyte, 1 mol/solution of LiClO ₄ dissolved in distilled dehydrated propylene carbonate was used.
It was used by impregnating the diaphragm 23, felt 24, and positive electrode mixture 25. Positive electrode mixture 25 contains 0.01 g of iron phthalocyanine ultrafine particles (average particle size 0.1 μm) and
A g-button black was formed by mixing with the above electrolyte. The battery thus produced was subjected to a discharge test at a constant current density of 2 mA/cm ² . FIG. 3 is a diagram showing the results of the discharge test. For comparison, the results of a discharge test of batteries made and measured under the same conditions using iron phthalocyanine powder polycrystals and phthalocyanine single crystals are also shown. In the figure, (a) shows the discharge characteristics of the battery according to the present invention, (b) shows the discharge characteristics of the battery using iron phthalocyanine powder polycrystal, and (c) shows the discharge characteristics of the battery using iron phthalocyanine single crystal. The metal phthalocyanine specific gravimetric energy density at 1V is 1270WH/Kg for each of the metal phthalocyanine ultrafine particle sample, powder polycrystalline sample, and single crystal sample.
They were 350WH/Kg and 270WH/Kg. Example 2 The same battery as in Example 1 was prepared, and a discharge test was conducted on this battery at a constant current density of 1 mA/cm ² . FIG. 4 is a diagram showing the results of the discharge test. For comparison, the results of a discharge test of batteries made and measured under the same conditions using iron phthalocyanine powder polycrystals and iron phthalocyanine single crystals are also shown. In the figure, a,
b and c are the same as in FIG. 3. The metal phthalocyanine specific gravimetric energy density at 1V end is 1780WH/Kg for each of the metal phthalocyanine ultrafine particle sample, powder polycrystalline sample, and single crystal sample.
They were 870WH/Kg and 430WH/Kg. Example 3 A battery identical to that of Example 1 was prepared, and a discharge test was conducted on this battery at a constant current density of 0.318 mA/cm ² . FIG. 5 is a diagram showing the results of the discharge test. For comparison, the results of a discharge test of batteries using iron phthalocyanine powder polycrystals and iron phthalocyanine single crystals produced and measured under the same conditions are also shown. In addition, in the figure,
a, b, and c indicate the same things as in FIGS. 3 and 4. The metal phthalocyanine specific gravimetric energy density at 1V is 2200WH/Kg for each of the metal phthalocyanine ultrafine particle sample, powder polycrystalline sample, and single crystal sample.
They were 1770WH/Kg and 1540WH/Kg. Example 4 The same battery as in Example 1 was prepared, and a discharge test was conducted on this battery at a constant current density of 0.1 mA/cm ² . FIG. 6 is a diagram showing the results of the discharge test. For comparison, the results of a discharge test of batteries made and measured under the same conditions using iron phthalocyanine powder polycrystals and iron phthalocyanine single crystals are also shown. Note that a, b, and c in the figure indicate the same ones as in FIGS. 3 to 5. The specific gravimetric energy density of metal phthalocyanine at 1V end is 2980WH/Kg for metal phthalocyanine ultrafine particle sample, powder polycrystalline sample, and single crystal sample, respectively.
They were 3520WH/Kg and 3690WH/Kg. Metal phthalocyanine ultrafine particle test a, powder polycrystal sample b, single crystal sample c of Examples 1, 2, 3, and 4
FIG. 7 shows the discharge current dependence of the specific gravimetric energy density in each battery. The ultrafine particle sample shows a high specific gravimetric energy density even at high discharge current, and its discharge voltage flatness is improved. Example 5 A battery similar to Example 1 was prepared using a positive electrode mixture formed by mixing 0.02 g of ultrafine iron phthalocyanine particles and 0.02 g of acetylene black with an electrolyte, and a constant current of 0.318 mA/cm ² was prepared. A charge/discharge test was conducted based on the density. The charge/discharge cycle is 3 hours of discharging, 40 minutes of rest, 3 hours of charging, and 40 minutes of rest, which is 150AH/Kg.
charge/discharge depth (corresponding to 3 electrons involved). That is, this curve shows a discharge state, then a rest period, then a charge state, then a rest period. It was possible to charge and discharge 61 times under conditions where the final charging voltage was 6V or less, at which the electrolyte decomposed. Example 6 0.01g of copper phthalocyanine ultrafine particles (average particle size
A battery similar to Example 1 was prepared using a positive electrode mixture formed by mixing 0.1 μm) and 0.01 g of acetin black with an electrolyte, and a charge/discharge test was conducted at a constant current density of 0.318 mA/cm ² . The charge/discharge cycle is 3 hours of discharge, 40 minutes of rest, 3 hours of charge, and 40 minutes of rest, which is a charge/discharge depth of 300 AH/Kg (corresponding to 6 electrons involved). FIG. 9 is a diagram showing the results of a charge/discharge test.
That is, this curve shows a discharge state, then a rest period, then a charge state, then a rest period. It was possible to charge and discharge 23 times under conditions where the final charging voltage was 6 V or less, at which point the electrolyte decomposed. Example 7 A battery similar to Example 1 was prepared using a positive electrode mixture formed by mixing 0.1 g of powdered polycrystalline and ultrafine particles of a metal or nonmetal compound having a phthalocyanine nucleus and 0.1 g of acetylene black with an electrolyte. death,
Constant current discharge tests at 0.318 mA/cm ² and 1 mA/cm ² were conducted. Table 1 shows each discharge capacity at a final voltage of 1V. However, Pc indicates a phthalocyanine nucleus.

【table】

[Table] As explained above, the lithium-phthalocyanine-based ultrafine particle battery of the present invention expands the effective reaction surface area by making the positive electrode active material into ultrafine particles, and can obtain a large current and has good discharge flatness. It has the advantage that it can be used in various fields as a secondary battery.

[Brief explanation of the drawing]

FIG. 1 shows an in-gas evaporation device for ultrafine metal phthalocyanine particles, and FIG. 2 shows a cross-sectional conceptual diagram of a cell for measuring characteristics of a button-type battery, which is an embodiment of the present invention.
3, 4, 5, and 6 are diagrams showing voltage changes during battery discharge in Examples 1, 2, 3, and 4 of the present invention, and FIG. 7 is a diagram showing voltage changes in Examples 1 and 2 of the present invention. Figures 8 and 9 show the discharge current dependence of the specific gravimetric energy density in Examples 5 and 4 of the present invention, and the number of charging and discharging cycles of the battery and the voltage change during charging and discharging in Examples 5 and 6 of the present invention. It is a diagram. 1... Vacuum chamber, 2... Ultrafine particle sample collection container, 3... Evaporation source, 4... Power source for evaporation source, 5
...regulator, 6...helium gas cylinder,
21... Container, 22... Lithium negative electrode, 23...
Diaphragm, 24...Felt, 25...Positive electrode mixture, 2
6...Teflon container, 27...Lead wire.

Claims (1)

[Claims] 1 As a positive electrode active material, ultrafine crystalline particles of a phthalocyanine compound with an average particle size of 1 μm or less formed by heating and evaporating a phthalocyanine raw material in a dilute inert gas atmosphere, lithium as a negative electrode active material, and a positive electrode active material and lithium as an electrolyte. Lithium is characterized by being composed of a material that is chemically stable and capable of moving because lithium ions undergo an electrochemical reaction with the positive electrode active material.
Phthalocyanine compound ultrafine particle secondary battery.