JPH0756795B2 - Electrode for non-aqueous secondary battery - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electron donating substance such as an alkali metal such as lithium, potassium and sodium, an alkaline earth metal, a rare earth metal or a transition metal and / or an electron such as a halogen or a halogen compound. The present invention relates to a non-aqueous secondary battery using an attracting substance as a charge carrier, and more particularly to an electrode structure for the non-aqueous secondary battery.

<Prior Art> In recent years, non-aqueous secondary batteries using alkali metals such as lithium have been attracting attention as electronic devices have been downsized and power consumption has been reduced, and they have reached the stage of practical application. However, in a battery in which a metal is used alone as an electrode, there is a problem that the negative electrode metal grows in a dendrite shape due to repeated charging / discharging, causing an internal short circuit, and it is extremely difficult to put it into practical use as a secondary battery. As an improvement measure, the development of a material that can absorb and release metal atoms such as lithium in the negative electrode is being advanced, and it is possible to efficiently absorb and release metal atoms such as metals such as low melting point alloys and organic materials. The material was found. However, any of the materials is in the form of powder, film, foil, fiber or the like, and when these are used to form an electrode, a step of fixing these materials to an electrode substrate serving as a current collector is required. For this reason, auxiliary materials such as a binder and a conductive material are required in addition to the charge carriers, and the capacity per unit weight or unit volume is reduced.

<Object of the Invention> In view of the above problems, an object of the present invention is to provide an electrode for a non-aqueous secondary battery, which has a high capacity and good charge / discharge repetitive characteristics without causing elution and decomposition.

<Outline of the Invention> The outline of the present invention is as follows. A carbon body is directly formed on a conductive substrate such as a three-dimensional structure having a high porosity as a carbon deposit from a hydrocarbon compound by a vapor phase deposition method (pyrolysis CVD method) by low temperature pyrolysis at 1500 ° C or less. An electrode is used as a carrier for charge carriers. Here, as the structure having a high porosity, a metal body having a three-dimensional structure generally called a foam metal, a cotton-like metal body, a reticulated metal body, a flat metal sintered body having a porosity of 60% or more, etc. is there. Further, as the carbon body, those obtained by vaporizing a carbon-hydrogen compound, particularly low-molecular aromatic or low-molecular unsaturated hydrocarbon, and depositing it from a low-concentration state through a low-temperature pyrolysis step are suitable. As a result of detailed analysis of the carbon body obtained in this way, it was found that it is a carbon material having a structure having a slightly disordered structure and a selectively oriented structure as compared with carbon having a highly oriented graphite structure. Obviously, the carbon material containing such a structure showed good characteristics as an electrode material using an alkali metal or the like as a dopant substance.

The characteristics of the carbon body will be described in more detail. Cu
When the layer spacing on the carbon plane was determined by the X-ray diffraction method using Kα rays, those having a layer spacing of 0.337 nm to 0.355 nm showed good characteristics as an electrode material. Further, the diffraction peak at that time does not show a sharp peak as seen in graphite, but shows a considerably wide diffraction peak. When the crystallite size in the C-axis direction is calculated using the method for determining the crystallite size from the half value of the diffraction peak, it is 2.0 nm to 10 nm.
It was in the range of 0.0 nm. The analytical peak of the (110) plane, which is reflected in the size of the crystallite in the ab axis direction, is almost nonexistent or very broad even if it appears, so the size of the crystallite in the ab axis direction is very small. Recognized to be.
The degree of progress toward graphitization was investigated by laser Raman spectroscopy. In addition to the Raman spectrum of 1580 cm ^-1 derived from the graphite structure, the Raman spectrum of 1360 cm ^-1 derived from the incompleteness of the graphite structure was observed, so this carbon material has an incomplete crystal structure compared to graphite. I understand. With the progress of graphitization, the peak at 1360 cm ^-1 decreases and the peak at 1580 cm ^-1 due to the lattice vibration peculiar to graphite increases.
Carbon body in the present invention, when viewed peak intensity ratio of 1360 cm ^-1 to the peak intensity of 1580 cm ^-1 in the Raman spectrum 0.
It is in the range of 4 to 1.0, and it can be said that the incompleteness of the graphite structure remains. The diffraction pattern of the reflected high-energy electron beam has a broad ring shape with the diffraction lines corresponding to the (002), (004), and (006) reflections of the graphite structure, which is reflected in the extremely fine crystallites. There is. A closer examination of these diffractive rings reveals that each ring is not uniform but has an arcuate or broad spot.
The orientation of each crystallite is not random, but (00
l) It was found that the faces are aligned in a particular direction. When this is further quantified, the relative inclination in the c-axis direction between the crystallites is within a range of ± 75 degrees, and the carbon material has an orientational arrangement mainly composed of the crystallites having the above orientation. Is characterized as a carbon material having

As described above, a carbon body having a larger interplanar spacing, a smaller crystallite size, and a certain degree of orientation with respect to each other as compared with graphite exhibits good characteristics as an electrode material. A carbon body that satisfies the above conditions is difficult to obtain by firing a powder body or a fibrous body. That is, even if the physical properties similar to those of the carbon body used in the present invention can be obtained in the plane spacing of the carbon body and the size of the crystallite, the orientation of each crystallite becomes irregular, and thus a large discharge capacity can be obtained. Therefore, it becomes difficult to withstand repeated charging and discharging over a long period of time.

The battery electrode of the present invention can be obtained by the following manufacturing method. Hydrocarbon compound which is a starting material hydrocarbon or a compound thereof in which a characteristic group containing at least one element selected from oxygen, nitrogen, sulfur or halogen is added or substituted, for example, benzene, naphthalene, anthracene, hexa Methylbenzene, 1,2-dipromoethylene, 2-butyne, acetylene, biphenyl, diphenylacetylene, etc. or other suitable carbon-based compounds are used, vaporized and supplied to the reaction system, and then placed on the conductive substrate. It is obtained by direct formation by a vapor deposition method by thermal decomposition at low temperature. The concentration and temperature for low-temperature pyrolysis vary slightly depending on the organic material used as the starting material, but are usually controlled to a concentration of several millimol% and a temperature of about 1000 ° C. As the vaporizing method, a bubbler method using hydrogen and / or argon as a carrier gas, an evaporation method or a sublimation method is used. Incidentally, when depositing the carbon body on the conductive substrate, a metal such as lithium may be simultaneously doped.

<Effects of the Invention> An electrode obtained by forming a carbon body on a conductive substrate such as a metal having high porosity by a vapor phase deposition method by low temperature pyrolysis is strong against a charge / discharge cycle and over discharge, Since it is not necessary to add such a conductive material, the packing density of the electrode is increased, resulting in high density characteristics. Also, because the process is simplified,
It is very effective as an electrode for non-aqueous secondary batteries. The battery obtained by using the electrode of the present invention has good charge / discharge cycle characteristics, and can be widely used in various fields as a small-sized and low-cost battery.

Furthermore, the invention of the present application uses a conductive substrate composed of a porous metal three-dimensional structure as a proposal, and carbon is directly deposited on the conductive substrate by vapor deposition. An electric effect can be obtained and a high capacity electrode can be obtained.

<Example> Hereinafter, the first example will be described with benzene as the hydrocarbon compound.
The present invention will be described in more detail with reference to the drawings.

A container 1 containing benzene which has been dehydrated and then subjected to distillation and purification by vacuum transfer is supplied with argon gas from an argon supplier 2 and a valve for benzene is operated to vaporize benzene particles together with the argon gas. It is fed to the quartz reaction tube 4 through the Pyrex glass tube 3. At this time, the temperature is kept constant by heating the container 1 by the amount of heat absorbed by the evaporation of benzene, and the opening / closing of the needle valves 5 and 6 is adjusted to optimize the amount of benzene. The reaction tube 4 has a diameter made of foamed nickel.
A sample holder 7 on which a conductive three-dimensional structure having a thickness of 15 mm and a thickness of 1.0 mm is placed is installed, and a heating furnace 8 is provided around the outer peripheral surface of the reaction tube 4. The sample holder 7 and the three-dimensional structure are heated and held at about 1000 ° C. by the heating furnace 8 to thermally decompose benzene supplied from the Pyrex glass tube 3. Carbon bodies are deposited on the three-dimensional structure by thermally decomposing benzene. The gas remaining in the reaction tube 4 after the thermal decomposition reaction is exhausted and removed by the exhaust equipment 9 and 10.

The X-ray diffraction diagram by CuKα line of the carbon body deposited on the conductive three-dimensional structure is shown in Fig. 2, and the Raman spectrum diagram is shown in Fig. 3.
Shown in the figure. From these figures, the average interplanar spacing of this carbon body is 0.
Is 342 nm, the ratio of the Raman intensity of 1360 cm ^-1 for the Raman intensity of 1580 cm ^-1 by Raman spectrum is found to be 0.75. The size of the crystallite in the c-axis direction determined from the X-ray diffraction peak in FIG. 2 was 4.86 nm according to the formula (1).

The diffraction pattern obtained by reflection high energy electron diffraction of a carbon body deposited on a conductive substrate placed on the same sample stage as the three-dimensional structure formed an arc-shaped broad ring. or,
The crystallite orientation determined from this diffraction pattern is such that the relative inclination of each crystallite in the c-axis direction is within ± 35 degrees, which indicates that the carbon body has a high orientation. Was confirmed. As for the natural graphite from Madagascar, when the X-ray diffraction pattern and Raman spectrum by CuKα were investigated in detail as with this carbon body, the average interplanar spacing was found.
Is 0.336 nm, the ratio of the scattering intensity of 1360 cm ^-1 relative scattering intensity 1580 cm ^-1 in the Raman spectrum was 0.1. Thus, there is a large difference in the Raman band of 1360 cm ^-1 , which is reflected in the disorder of the crystal structure in the graphite structure even if there is no great difference in the average interplanar spacing, the carbon body used in this example, the graphite such as natural graphite It can be seen that it has a slightly disordered structure.

An electrode body composed of a carbon body obtained by directly forming on the conductive substrate from the gas phase by low-temperature pyrolysis and a three-dimensional structure as the substrate was molded by a press machine to obtain an electrode A. A charge / discharge test was conducted by a three-electrode method in which this electrode A was used as a test electrode and lithium was used as a reference electrode and a counter electrode, using a propylene carbonate solution containing 1M lithium perchlorate as an electrolytic solution. In order to compare the characteristics of the electrodes obtained in the above-mentioned examples, benzene was pyrolyzed by using the reaction apparatus of FIG. 1, a carbon body was deposited on a quartz substrate, and then this was taken out and ground into powder. Then, 20 parts by weight of polyethylene powder as a binder is added to 100 parts by weight of the carbon body and uniformly mixed. Next, it was filled into a three-dimensional structure made of foamed nickel and having a diameter of 15 mm and a thickness of 1.0 mm, kept at a temperature of 150 ° C., and 300 kgcm ^-2 using a press machine.
An electrode B was produced by compression molding under the pressure of. This electrode B was also subjected to the charge / discharge test under the same conditions as the electrode A. FIG. 4 is a characteristic diagram showing charge / discharge characteristics of the electrode A (shown by the solid line of the curve A) and the electrode B (shown by the broken line of the curve B) of this example. From the results, it was confirmed that when the electrodes having the same shape were compared, the electrode A according to this example had a larger electric capacity. Thus, by directly forming the carbon body as the electrode active material on the conductive substrate by vapor deposition, an electrode having a high capacity and a simplified manufacturing process can be obtained.

Using the electrode produced by the above process as one of the negative electrode or the positive electrode, the other electrode cation or anion-doped conductive material for example _{^{Li +, K +, ClO 4}} -, BF 4 -
Etc. doped with a high polymer such as polyacetylene, composed of nickel chloride zinc intercalation compound, MnO ₂ , Bi
Capable of charging and discharging using metal oxides such as ₂ O ₃ and Cr ₃ O ₈ and other various electrode materials, and non-aqueous electrolytes such as lithium nitride, beta-alumina and organic electrolytes. A secondary battery. Both electrodes may use the carbon material produced in the above process.

Since the battery of this embodiment uses the electrode having good charge / discharge characteristics shown in FIG. 4, it has a long life in repeated use and high reliability is ensured for a long time.

[Brief description of drawings]

FIG. 1 is a block diagram of a carbon body producing apparatus used to explain one embodiment of the present invention. FIG. 2 is an X-ray diffraction diagram by a CuKα ray of the carbon body used in the electrode A shown in the example of FIG. FIG. 3 is a laser Raman spectrum diagram of the carbon body used in the electrode A shown in the embodiment of FIG. FIG. 4 is a charge / discharge characteristic diagram of the electrode A and the electrode B for comparison. 1 ... Benzene container, 2 ... Ar gas feeder, 3 ... Pyrex glass tube, 4 ... Quartz reaction tube, 5, 6 ... Needle valve, 7 ... Sample holder, 8 ... Heating furnace.

Front page continuation (72) Inventor Motoo Mohri 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Prefecture Sharp Corporation (72) Yoshikazu Yoshimoto 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka In-house (56) Reference JP-A-60-36315 (JP, A) JP-A-59-18578 (JP, A) JP-A-50-50629 (JP, A)

Claims (3)

[Claims] 1. A carbon body vapor-deposited on a conductive substrate composed of a porous metal three-dimensional structure has a peak intensity of 1580 cm ^{−1 in} an argon laser Raman spectrum.
An electrode for a non-aqueous secondary battery, having a hexagonal graphite layer structure having a disordered layer structure having a peak intensity ratio of 60 cm ^-1 in the range of 0.4 to 1.0. 2. The average interplanar spacing of the hexagonal mesh of the carbon body is 0.33.
The non-aqueous secondary battery electrode according to claim 1, which has a thickness of 7 nm to 0.335 nm. 3. The electrode for a non-aqueous secondary battery according to claim 1, wherein the conductive substrate made of the porous metal three-dimensional structure is a porous substrate having a porosity of 60% or more.