JPH03266358A - Manufacture of carbon electrode and nonaqueous secondary battery - Google Patents

Abstract

PURPOSE:To improve the adhesion between a carbon film and a base plate by thermally decomposing hydrocarbon or a hydrocarbon compound by gas phase to accumulate a thermally decomposed carbon on a conductive base plate having a plurality of projection parts on at least one surface thereof in such a manner that C-axis is parallel to the base plate surface. CONSTITUTION:On a conductive base plate having a plurality of projection parts on at least one of both the surfaces thereof, hydrocarbon or a hydrocarbon compound is thermally decomposed by gas phase to accumulate a thermally decomposed carbon. The projection part may have any one of fibrous, needle, cylindrical and rectangular forms. The length of the projection part is 0.05-0.5mm. The density of the projection part is generally 10-100 pieces per cm<2>. As the hydrocarbon compound, those in which a specified group containing at least one element selected from oxygen, nitrogen, sulfur or halogen is added to or substituted for a part of hydrocarbon are used.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention provides a method for manufacturing a carbon electrode that has a high capacity, a long cycle life, and is capable of discharging a large current, and a method for using the carbon electrode manufactured thereby. This relates to non-aqueous secondary batteries.

<Prior art> Carbon electrodes, in which pyrolyzed carbon is deposited on a conductive substrate by vapor-phase pyrolysis of legalized hydrogen, are excellent as negative electrode active materials for secondary batteries using alkali metals such as lithium. (For example, Japanese Patent Laid-Open No. 63-102167).

For example, in the case of lithium secondary batteries, if metallic lithium alone is used as an electrode, problems such as a reduction in charge/discharge cycle characteristics due to a passive film on the surface and internal short circuits due to dendrite growth during charging occur. Then such a problem will not occur. Furthermore, by using the above carbon electrode, a negative electrode-dominated battery (Japanese Patent Laid-Open No. 63-13282) can be produced. For this reason, when the above carbon electrode is used, a secondary battery with little deterioration in cycle characteristics and strong resistance to overdischarge can be produced.

Conventionally, the carbon electrode described above has been produced by depositing pyrolytic carbon on a planar substrate.

<Problems to be Solved by the Invention> However, conventional carbon electrodes are not fully satisfactory in terms of capacity density, current characteristics, and cycle life.

This is because a carbon film having strong C-axis orientation is deposited in the direction perpendicular to the substrate surface. That is, the pyrolytic carbon has a graphite structure, and a dopant such as a lithium atom constituting the active material is inserted between its layers. Therefore, in the case of a carbon film in which the C axis is perpendicular to the substrate surface, there is no entrance of the dopant into the interlayer, and insertion of the dopant is less likely to occur. This causes deterioration of various characteristics such as charging and discharging characteristics at large currents.

Furthermore, in the carbon electrode, the insufficient adhesion between the carbon film and the substrate is a cause of the inability to obtain the above-mentioned sufficient characteristics. This is because insufficient adhesion causes a decrease in current collection efficiency, and the carbon film falls off from the substrate during cycling.

In view of the above, the present invention aims to deposit pyrolytic carbon on a substrate so that the C axis is parallel to the substrate surface, and to improve the adhesion between the carbon film and the substrate.

1. The purpose of the present invention is to provide a secondary battery using a carbon electrode obtained by solving the above problems.

<Means for Solving the Problems> In order to solve the above problems, in the present invention, hydrogen hydroxide or hydrocarbon A method for manufacturing a carbon electrode is provided, which comprises depositing pyrolytic carbon by thermally decomposing a compound in a gas phase.

The shape of the protrusion may be any shape, such as fibrous, acicular, cylindrical, or rectangular parallelepiped. Further, the length of the protrusion is 0.05 to 0.5 fl, preferably 0.1 to 0.
21111 is desirable. It is desirable that the density of the protrusions be high, but it is usually about 10 to 100, preferably about 30 to 80 per 1 d. As a hydrocarbon compound,
Hydrocarbons to which a characteristic group containing at least one element selected from oxygen, silicon, sulfur, or halogen is added or substituted are used. The conductive substrate is more preferably one containing a metal, such as iron, cobalt, or nickel, that has a catalytic effect on the production of pyrolytic carbon. Here, the catalytic action refers to the action of increasing the crystallinity of the graphite structure of the pyrolytic carbon deposited on the substrate or the action of increasing the deposition rate of the pyrolytic carbon.

Further, the present invention is characterized in that, using the carbon electrode obtained by the above manufacturing method, a positive electrode body, a separator, and a negative electrode body are laminated so that the surface provided with the protrusion portion faces the positive electrode with a separator in between. We provide non-aqueous secondary batteries.

<Function> According to the present invention, even if a carbon film having strong C-axis orientation is deposited in the direction perpendicular to the substrate surface due to thermal decomposition of hydrocarbons, the protrusions remain at a constant level with respect to the substrate surface. Because of the angle, the carbon film deposited on the side surface of the protrusion will cause interlayer gaps to appear on the electrode surface.Furthermore, if the angle of the protrusion has an appropriate angle, the carbon film deposited on the side surface of the protrusion will appear on the electrode surface. When the C-axis orientation is parallel to the C-axis, insertion of a dopant such as lithium becomes easier. Furthermore, the presence of the protrusions improves the adhesion of the carbon film to the substrate.

On the other hand, in the battery of the present invention, since the surface provided with the protrusion faces the positive electrode body, the gap between the layer surfaces of the layered pyrolytic carbon that constitutes the carbon electrode faces toward the positive electrode body. As a result, reversible intercalation and deintercalation of alkali metals, etc. proceed smoothly and efficiently.

<Example> The present invention will be explained in more detail with reference to Examples.

Example: A nickel foil serving as a planar substrate 2 with a thickness of 0.1 fl was coated with 0.
．． A substrate 1 on which 930 nickel wires with a diameter of 3 fl and a height of 0.2 fl are protruded per square centimeter on one side as protrusions 3.
Finished with precision casting. FIG. 1 is a schematic structural diagram of this substrate. Here, the carbonaceous material serving as the negative electrode was produced using a reaction apparatus shown in FIG.

That is, - Argon gas is supplied from an argon gas supply device 12 into a container 11 containing benzene that has been subjected to a dehydration treatment and further subjected to a distillation purification operation by vacuum transfer. The hebenzene is fed through the quartz reaction tube 14. At this time, the temperature is kept constant by heating the container 11 by the amount of heat absorbed by the evaporation of benzene, and the needle valve 15.
The amount of benzene was optimized by operating No. 16.

A holder 17 on which a 2σ×1α substrate 1 is mounted is installed in the reaction tube 14K, and a heating furnace 18 is provided around the outer periphery of the reaction tube 14. The holder 17 and the electrode substrate 1 are held at about 1000° C. for about 1 hour in the heating furnace 18, and the benzene supplied through the Pyrex glass tube 13 is thermally decomposed, and 10.8 mg of pyrolyzed carbon is added to the electrode substrate. deposited.

The gas remaining in the reaction tube 14 after the pyrolysis reaction is removed through exhaust equipment 19,20. The electrical substrate on which carbon was deposited in this manner was used as the electrode of this example. A charge/discharge test was conducted using a three-electrode method using this electrode as a test electrode, lithium as a reference electrode, and counter birch using a propylene carbonate solution containing IM lithium perchlorate as an electrolyte. Note that the substrate was arranged so that the protrusion 3 faced the opposite electrode.

FIG. 3 is a diagram showing the relationship between discharge capacity and discharge time rate.

The curve labeled A in FIG. 3 shows data for this electrode. The curve labeled B in FIG. 3 shows data for the reference electrode. This reference electrode has a thickness of 0.111+ on the substrate.
It was made in the same manner as in the above example except that a conventional nickel foil of 11.2 an x 1 c + n was used, and 9.6 mg of pyrolytic carbon was deposited.

Note that the measurements were performed in the same manner as for the electrodes in the above examples.

From the data shown in Figure 3, the electrode according to this example has superior large current discharge characteristics compared to the conventional comparative electrode, and has a substantially larger capacity for discharge at large current. It can be seen that it has.

Furthermore, compared to the comparative electrode, the carbon film had better adhesion to the electrode of this example, and its cycle characteristics were also excellent. Furthermore, it was found that the current collection efficiency was good and the resistance component of the electrode was small.

Next, using the carbon electrode of this example, a secondary battery was produced in a paper mold, which is an example of the non-aqueous secondary battery of the present invention. FIG. 4 is a schematic structural diagram of a secondary battery in this paper mold.

This battery is constructed by using the carbon film j of this example as a negative electrode body 4, and a positive electrode body 5 made of ■205 is placed with a separator 6 in between. ,
It faces the positive electrode body 5. In addition, 1. -11
Propylene carbonate containing various types of LiCIO4 was used. The thickness of this battery including the outer plate 7 of the stainless steel container is 0.9fi. The opening is sealed with a resin sealing body 8.

For comparison with the battery of this example, a battery a using the same carbon electrode as that of this example and with the surface provided with the protrusion 3 facing opposite to that of this example, and a battery prepared by the conventional method described above were prepared. A battery cell was fabricated using the reference electrode as a negative electrode body. Batteries a and b had the same structure as the battery according to this example except for the negative electrode body.

When these batteries were compared, the battery of this example was the most excellent in charge/discharge characteristics at large currents, followed by the battery.

The battery shown above has a structure in which the positive electrode body, separator, and negative electrode body are laminated one by one, but when each component is further laminated and the positive electrode body is placed on both sides of the negative electrode body, A carbon electrode is manufactured using a substrate having protrusions on both sides, and the surface of the negative electrode body provided with the protrusions is directed toward both positive electrode bodies on both sides of the negative electrode body. It is better to have a structure.

<Effects of the Invention> By manufacturing a carbon electrode by the method of the present invention, a carbon electrode that can easily and reversibly intercalate and deintercalate alkali metals etc. can be manufactured. , high capacity, long cycle life, and
A secondary battery capable of large current discharge can be provided.

Further, according to the battery of the present invention, it is possible to provide a non-aqueous secondary battery that maximizes the characteristics of the carbon electrode manufactured by the method of the present invention.

[Brief explanation of drawings]

Fig. 1 is a schematic structural diagram of a substrate used in an example of the present invention, Fig. 2 is a diagram of a reaction apparatus used in an example, Fig. 3 is a diagram showing the relationship between discharge capacity and discharge time rate, and Fig. 4 This is a schematic diagram of the battery used in the paper mold of this example. 1... Substrate 2... Planar substrate 3... Protrusion 4... Negative electrode body 5... Regular body 6-... Separator

Claims (1)

[Claims] 1. Pyrolytic carbon is deposited by thermally decomposing a hydrocarbon or a hydrocarbon compound in a gas phase on a conductive substrate having a plurality of protrusions on at least one side of a flat substrate. A method for manufacturing a carbon electrode, characterized by: 2. A positive electrode body, a separator, and a negative electrode body are laminated, and the negative electrode body is the carbon electrode according to claim 1, and the carbon electrode has a surface provided with the protrusion facing the positive electrode body. A non-aqueous secondary battery characterized by: