JPS63124380A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PURPOSE:To increase charge-discharge cycle performance in deep charge by using carbon family active material mainly comprising carbon as a negative active material and organic polymer active material mainly comprising conductive organic polymer as a positive active material. CONSTITUTION:A negative electrode 11 uses carbon in which a Raman spectrum intensity ratio of 1360cm<-1> to 1580cm<-1> is 0.4-1.0, a mean spacing of plane network six-membered ring is 0.337-0.355nm, and a crystallite size in c-axis direction is 2.00-10.00nm. A positive electrode 12 uses, as an active material, a conductive organic polymer which forms a charge-transfer complex, which is electrochemically reversible, with an electron acceptor such as halogen and halogen compound and is n-type conductive organic polymer, such as polyacene, polyacenoacene, polyacetylene, and polymethyl acetylene.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a non-aqueous electrolyte secondary battery. More specifically, it uses light metal cations, which are electron-donating substances such as lithium and sodium, and anions, which are electron-withdrawing substances such as halogen and halogen compounds, as charge carriers, and uses an aprotic organic solvent as a solvent for the electrolytic solution. The present invention relates to a water electrolyte secondary battery.

(b) Conventional technology Battery systems that use light metals such as lithium as active materials can obtain high voltage and have high energy density, so they can be used in a wide range of applications, such as power sources for small electrical devices and memory backup power sources. There are many application fields, and the development of wider applications is being promoted. However, since metallic lithium foil, ingot, etc. are used for the negative electrode, there are problems such as a decrease in the volume of the lithium negative electrode due to discharge, and internal short circuits of the battery due to lithium dendrites that occur due to repeated charging and discharging, making it difficult to develop applications for secondary batteries. It was difficult to use, and its application was limited to secondary batteries. However, with the development of demand for portable small electric devices and the like, there are increasing expectations for the conversion of lithium batteries into secondary batteries.

(c) Problems to be solved by the invention In order to use a lithium battery as a secondary battery, charging and
The battery must not change its characteristics even after repeated discharges, that is, it must not suffer from deterioration in cycle characteristics.

Conventionally, when metallic lithium is used for the negative electrode, the discharge capacity of the negative electrode is made significantly larger than that of the positive electrode in order to prevent the formation of lithium dendrites in the negative electrode, which occurs when charging and discharging are repeated. Attempts are being made to lower the usable range of negative electrodes. However, when lithium metal is used alone as an electrode, the volume of the electrode decreases due to discharge, and as a result, the current collection effect deteriorates, which causes an increase in the internal resistance of the battery. From this perspective, research has been carried out on materials that can reversibly absorb and release light metals such as lithium for negative electrodes. Internal short circuit of the battery due to the occurrence of
It has become possible to prevent deterioration of the current collection effect due to a decrease in electrode volume. However, even in batteries using such materials,
Repeated charging and discharging cycles undeniably caused deterioration of the negative electrode due to embrittlement, elution, etc., and further improvements were needed for the negative electrode.

Furthermore, when an active material such as a metal oxide or a metal chalcogen compound is used as the positive electrode and the above-mentioned material is used as the negative electrode and discharge is performed, the metal in the positive electrode goes through multiple stages from a high oxidation state to a low oxidation state. Change the oxidation number. Due to the discharge reaction, lithium cations in the nonaqueous electrolyte penetrate into the positive electrode active material. These lithium cations can be easily extracted from the positive electrode active material while the metal in the positive electrode is in a highly oxidized state, but as the discharge progresses, the amount of lithium cations in the positive electrode active material increases, and the positive electrode When the metal inside shifts to a low oxidation state, the positive electrode active material takes in lithium ions in a stable state, making it difficult to extract lithium cations from the positive electrode active material. In other words, when deep discharge is performed using compounds such as metal oxides and metal chalcogen compounds as positive electrode active materials, light metal ions, which are charge carriers, are captured in a stable state, forming stable compounds that are difficult to release. I end up.

Therefore, when compounds such as metal oxides and metal chalcogen compounds are used as positive electrode active materials, charging and
Repeating discharge cycles will promote a decrease in discharge capacity.

On the other hand, organic polymers with conjugated double bonds such as polyacetylene and organic polymers with a polyacene skeleton structure can be used to electrochemically reversibly react with anions such as lithium perchlorate ions, hexafluoride and acid ions, and boron tetrafluoride ions. It is known that it forms charge transfer complexes with ions and cations such as lithium ions and sodium ions, and can become p-type and n-type conductive organic polymers. Electrodes using these organic polymers as active materials have high capacity density and high current density.
In addition, it is attracting attention as an electrode for secondary batteries because of its good repeatability in charge/discharge cycles. However, when these organic polymers are used as a negative electrode, that is, an electrode that forms a charge transfer complex with light metal ions such as lithium ions and sodium ions, there is a problem that dendritic precipitation of light metals occurs during charging, which causes internal short circuits in the battery. was there.

The present invention was made in view of this situation, and an object thereof is to provide a non-aqueous electrolyte secondary battery that does not reduce its discharge capacity even after repeated charge/discharge cycles involving deep discharge and has an excellent cycle life. It is something to do.

(d) Means for solving the problem The inventors of the present invention first focused on the use of carbon, which is an electrode active material that does not have to worry about elution or decomposition, as a negative electrode material, and conducted intensive research from the above viewpoint. As a result, the carbon body formed on the support by subjecting hydrocarbon compounds such as benzene to pyrolytic CVD (vapor phase deposition method) at 1500°C or less,
The fact that the carbon body has a planar network-like six-membered ring structure that has a slightly more turbostratic structure and selective orientation than the conventional highly oriented carbon body that has a graphite structure, and that the carbon body that has this turbostratic structure is different from the conventional carbon body that is Oriented pyrolytic graphite, natural graphite, organic edge = 8
- It has been found that electrochemically reversible doping and dedoping of light metals such as lithium occurs more easily and the electric capacity is larger than that of fibers such as carbonized graphite and activated carbon. As a result of further investigation, we found that the specific carbon material described above can be used as an electrode active material to form a negative electrode body, and electrolyte anions (electron-donating substances) such as perchlorate ions can be electrochemically reversible. By constructing a positive electrode body using a conductive organic polymer doped as a charge transfer complex as an electrode active material, a non-aqueous electrolyte secondary battery that can discharge to a deep discharge depth and has significantly improved charge-discharge cycle characteristics has been created. Based on these findings, we have completed the present invention.

Thus, according to the present invention, there is provided a non-aqueous electrolyte secondary battery using a non-aqueous electrolyte containing light metals such as lithium and sodium as active materials and disposing a negative electrode body and a positive electrode body with a separator interposed therebetween. As the electrode active material of the negative electrode body,
The average interplanar spacing is 0.337 to 0.355 nm, and the Raman intensity ratio of 1360cIn-1 to 1580aa-'' in the argon laser Raman spectrum is 0.4 to 1.
．． A carbon-based active material whose main component is a carbon body with a planar network six-membered ring structure having zero and selective orientation, and which is electrochemically reversible with an electron-accepting substance as the electrode active material of the positive electrode body. A nonaqueous electrolyte secondary battery is provided that uses an organic polymer active material whose main component is a conductive organic polymer capable of forming a charge transfer complex.

The above-mentioned specific carbon body in the present invention can be formed into a predetermined electrode support by CVD (vapor phase deposition) using low-temperature pyrolysis at 1500° C. or lower from a hydrocarbon compound.

Examples of the hydrocarbon compounds include aliphatic hydrocarbons (preferably unsaturated hydrocarbons), aromatic hydrocarbons, and alicyclic hydrocarbons, which have substituents (e.g., halogen atoms, hydroxyl groups, sulfonic acid groups, nitro group, nitroso group, amine group, carboxylic acid group, etc.). Specific examples include benzene, naphthalene, anthracene, hexamethylbenzene, 1,2-dibromoethylene, 2-butyne, acetylene, biphenyl, diphenylacetylene, etc. Among these, aromatic hydrocarbons such as benzene are used. is preferable. In addition, the concentration and temperature of the compound in the gas phase to be thermally decomposed vary depending on the hydrocarbon compound used as the starting material, but usually the concentration is several mmol percent, and the temperature is 1 mmol percent.
It is appropriate to control the temperature to about 000°C. Also,
As a method of vaporizing the hydrocarbon compound to supply it as a gas into the CVD chamber, a bubbler method using hydrogen and/or argon as a carrier gas, a distillation method, a sublimation method, etc. can be selected as appropriate depending on the boiling point of the hydrocarbon. do it.

On the other hand, the support on which the carbon body is formed can be directly an electrode support, in which case at least the pyrolytic carbon
Porous, mesh, cross, net, nonwoven, or other forms having heat resistance that can withstand the temperature during VD are suitable. The material of this support may be an electrical insulator or an electrical conductor. Usually a quartz glass plate,
It is suitable to use nickel net or the like. However, the carbon body may be separated from the support and combined with a new electrode support.

The carbon body formed in this way has a slightly more turbostratic structure than carbon, which is composed of a highly oriented graphite structure,
Moreover, it is mainly composed of carbon having a selectively oriented structure, and has the above-mentioned physicochemical properties. Here, the interplanar spacing of 0.337 to 0,355 nm is a value determined by X-ray diffraction method, and the crystallite size in the C-axis direction of the crystallite is determined from the half-width of this diffraction peak. The size is from 2.00 nm to 10. It is preferable that it is OOnm. Further, the orientation of the carbon body can be determined by reflection high-speed electron diffraction. This diffraction pattern has a broad ring shape, reflecting the fact that the crystallites are very small. To explain in more detail, a broad ring is not uniform but has an arc shape or a broad spot, and the relative inclination of each crystallite in the C-axis direction is within a range of ±75 degrees, preferably within a range of ±60 degrees. It can be characterized as

That is, the carbon body has a planar network six-membered ring plane spacing of 0.3.
37nn+ to 0.355nm, which is somewhat longer than the 0.335nm of natural graphite (for example, from Madagascar). Furthermore, the half-width of the diffraction peak is considerably wider than that seen in graphite, for example, 2θ=2.0'. As described above, since the spacing between the six-membered ring planes in the planar network is slightly wider than that of natural graphite, it is possible to form electrochemically reversible intercalation compounds with light metals such as lithium and sodium which are electron donating substances.

In addition, the Raman scattering method is generally used as an indicator to know the progress of graphitization, and in general, carbon materials having a planar network-like six-membered ring surface are attributable to stretching vibrations of the planar network-like six-membered ring surface in the vicinity of 1360an-'. Surumann scattering peak and 1580an
There is a scattering peak near -' that is attributable to the vibration of the planar reticular six-membered ring planes. With the progress of graphitization of carbon materials1
The peak at 360 cm-' decreases and the peak at 1580 aa-' increases. The carbon body used in the present invention is 15
The ratio of the Raman intensity of 1360 rho1 to the Raman intensity of 80 an-' is between 0.4 and 1.0, and lithium,
It is an excellent carbon material that forms electrochemically reversible intercalation compounds with light metals that are electron-donating substances such as sodium.

Also, a method for determining the size of crystallites in the C-axis direction, which corresponds to the perpendicular direction of the plane network six-member ring plane, from the half-width of the X-ray diffraction peak of the (002) plane of carbon having a plane network six-member ring plane. According to the above, the average interplanar spacing of the planar reticular six-membered ring surface is 0.
337 nm to 0,355 nm, and the crystallite size in the C-axis direction, which corresponds to the vertical direction of the planar reticular six-membered ring plane, is from 2,00 nn+ to 10. OOnm exhibits better properties. The diffraction peak of the (110) plane in the ab-axis direction, which corresponds to the horizontal direction of the plane network six-membered ring plane, rarely appears or is very broad, so the crystallites in the ab-axis direction It also turns out to be small.

On the other hand, the orientation determined from the diffraction peak obtained by reflection high-speed electron diffraction, which is often used as a means of examining the orientation of carbon materials, is the C between each crystallite.
A carbon body in which the relative inclination in the axial direction is defined within a range of ±15 degrees exhibits good characteristics. A ring-shaped diffraction pattern with a broad diffraction pattern exhibited particularly good characteristics, and a diffraction pattern in which the ring was not uniform but had an arc shape or a broad spot showed good characteristics. These rings are made of (002) carbon material having a planar network six-membered ring surface.
The (004) and (006) plane reflections are the main ones, and due to the shape of the ring, the C axes of each crystallite in the carbon body are well aligned in the characteristic direction.

The conductive organic polymer used as the positive electrode active material of the secondary battery of the present invention forms an electrochemically reversible charge transfer complex with an electron-accepting substance such as a halogen or a halogen compound, and forms an n-type conductive organic polymer. Any organic polymer having a boriacene skeleton structure such as polyacene, polyacenoacene, polyphenanthrene, polyperylene, polyphenanthrene, polyacetylene, polymethylacetylene, polyphenylacetylene, polychlorophenylacetylene, polydiacetylene, etc. may be used as long as it can be a polymer. Examples include polymers having one-dimensional conjugated double bond chains such as polyphenylene, polyphenylene sulfide, polydiphenylene sulfide, poly-paraphenylene sulfide, polyaniline, polypyrrole, polyindole, polythiophene, and polyfuran. The organic polymer having a polyacene skeleton structure is obtained by heat-treating a polymer resin having an aromatic ring such as a phenol resin at a temperature of about 800°C in an inert atmosphere such as nitrogen, argon, helium, etc. A polymer having a dimensional conjugated double bond chain is obtained by polymerizing monomers of the polymer by a method such as thermal polymerization or electrolytic polymerization.

A positive electrode body can be constructed by coating or impregnating a suitable support similar to the electrode support of the negative electrode body described above with these conductive organic polymers.

Examples of the non-aqueous electrolyte for the secondary battery of the present invention include dimethyl sulfoxide, γ-butyral lactone, propylene carbonate, sulfolane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,2-dimethoxyethane, 1,
A monomer obtained by dissolving a salt having a light metal ion as a cation such as lithium perchlorate, lithium hexafluoroarsenate, lithium borofluoride, or lithium trifluoromethanesulfonate as an electrolyte in an aprotic organic solvent such as 3-dioxolane. A single solution or a mixture of solutions can be used.

However, the electrolyte includes a cation that can form an electrochemically reversible intercalation compound with the carbon material used in the negative electrode of the battery, and a charge transfer complex that forms an electrochemically reversible charge transfer complex with the organic polymer used in the positive electrode of the battery. Any material may be used as long as it contains the anion to be obtained. Further, the solvent may be any aprotic organic substance as long as it can dissolve the above-mentioned electrolyte.

The separator of the secondary battery of the present invention has electrical insulation properties such as polyethylene resin, polypropylene resin, glass wool, glass paper, ceramic paper, etc.
In addition, any material may be used as long as it has the ability to hold the electrolyte and does not react with the battery components.

(e) Function The electrode active material of the negative electrode body is composed mainly of a carbon body having a slightly turbostratic structure and a selectively oriented structure, rather than a carbon body consisting of a highly oriented graphite structure. Doping and undoping of light metal active material ions such as lithium and sodium in the electrolytic solution is performed smoothly, and the electric capacity is improved. On the other hand, since an organic polymer active material whose main component is a conductive organic polymer that can form an electrochemical charge transfer complex with an electroreceptive substance is used as the electrode active material of the positive electrode, halogen Doping and undoping of anions such as ions is also smoothly performed, and the effects of these negative and positive electrode bodies work together to improve various discharge characteristics.

(F) Examples Example 1 The negative electrode active material has a carbon body formed by low-temperature pyrolysis using benzene as a starting material, and the positive electrode active material has a polyacene-based skeleton structure obtained by high-temperature polymerization of a phenol resin. Example 1 is a nonaqueous electrolyte secondary battery using an organic polymer, a polyethylene resin for the separator, and propylene carbonate in which 1M lithium perchlorate is dissolved in the electrolyte. Explain in detail.

A carbon body, which is a negative electrode active material, was produced using the reaction apparatus shown in FIG. - First, argon gas is supplied from the argon gas supply device 2 into the container 1 containing the benzene that has been dehydrated and then subjected to the distillation purification operation by vacuum transfer, and the benzene is bubbled to form a Pyrex glass tube 3. Hebenzene was fed through four quartz reaction tubes. At this time, the temperature is kept constant by heating the container 1 by the amount of heat absorbed by the evaporation of benzene.
The amount of benzene was optimized. The reaction tube 4 is made of foamed nickel and has a diameter of 15 mmφ and a thickness of 1 and 5 mm.
A holder 7 on which a three-dimensional structure (electrode support) with a diameter of
are provided around the area. The holder 7 and the three-dimensional structure were maintained at approximately 1000° C. in the heating furnace 8, and the benzene supplied from the Pyrex glass tube 3 was thermally decomposed, and carbon bodies were deposited on the three-dimensional structure over a period of 60 minutes. . The gas remaining in the reaction tube 4 after the pyrolysis reaction was removed through exhaust equipment 9.10.

The three-dimensional structure in which the carbon bodies obtained in the above steps were deposited was molded using a press machine to form the negative electrode body of the battery of Example 1.

X using the CIIKα line of the carbon body obtained here as a light source
A line diffraction diagram is shown in Figure 2, and a Raman spectrum diagram using an argon laser is shown in Figure 3. From these figures, the average interplanar spacing of the carbon body of this example is 0.345 nm, and the ratio of the Raman intensity at 1360 ao-1 to the Raman intensity at 1580 mm' according to the Raman spectrum is 0.80.
It can be seen that it is. Further, the size of the crystallite in the C-axis direction determined from the half-width of the diffraction peak in the X-ray diffraction diagram shown in FIG. 2 was 2.72 nm.

The diffraction pattern obtained by reflection high-speed electron diffraction has a broad arcuate ring. The orientation of the crystallites determined from this diffraction pattern is such that the relative inclination of each crystallite in the C-axis direction is within ±18 degrees, and has high orientation. Regarding natural graphite from Madagascar,
When X-ray diffraction and Raman scattering experiments were conducted, the average interplanar spacing was 0.336 nm, and the ratio of the Raman intensity at 1360 cm-'' to that at 1580 cnI-1 was 0.1. From the result, 0
, 342 nm, and 0,336 nm, but the ratio of the Raman intensity at 1360 cm-'' to the Raman intensity at 1580 cm-'' due to Raman scattering is ol.
There is a clear difference between go, o, and i, and it can be seen that the two are structurally different.

Regarding the carbon body having a graphite structure, the Raman peak at 1360 cm-' obtained by the Raman scattering method is attributed to a peak that reflects the disorder of the crystal structure. It has a layered structure.

That is, it was found that the carbon body in this example was a carbon body whose main component was carbon having a slightly turbostratic structure rather than carbon having a highly oriented graphite structure.

An organic polymer having a polyacene skeleton structure, which is a positive electrode active material, was prepared in the following order.

A solution was prepared by mixing an aqueous resol type phenolic resin with a concentration of about 65%, water, and zinc chloride in a weight ratio of 2:1:5. This solution was impregnated into phenol fibers that had been heat treated in advance at 300° C. for 4 hours in an inert atmosphere. This mixed solution impregnated fiber was heated to 100°C.
Pressure was applied and molded for about 10 minutes using a pressure molding machine maintained at a temperature of about 500. A composite molded body having a thickness of i was obtained. This composite molded body was heated to 550° C. at a temperature increase rate of about 40° C. per hour in an inert atmosphere to perform heat treatment. After cooling this heat-treated product to room temperature, it was washed with boiling water for about 5 hours to remove remaining zinc chloride and dried under reduced pressure using a rotary pump at a temperature of 120°C. A positive electrode body was obtained. Regarding the positive electrode body, XRF (
When chlorine and zinc were analyzed using a fluorescent X-ray analyzer, only peaks as traces of chlorine and zinc were observed. That is, it was found that almost no zinc chloride remained in the positive electrode active material.

When the positive electrode body was subjected to X-ray diffraction using the CuKα line, broad peaks were present at 20° to 22° and 416° to 46° in 2θ, and it was confirmed that the positive electrode body had a polyacene skeleton structure.

Example 2 A carbon body formed by low-temperature pyrolysis using benzene as a starting material was used as the negative electrode active material, polyaniline was used as the positive electrode active material, and polyethylene resin was used as the separator.
The present invention will be described by producing a non-aqueous electrolyte secondary battery using propylene carbonate in which 1M lithium perchlorate is dissolved in the electrolyte.

A carbon body serving as a negative electrode active material was produced in the same manner as in Example 1, and was used as the negative electrode body of the battery of Example 2.

A polyaniline electrode, which is a positive electrode active material, was produced by an electrolytic polymerization method as shown below.

Polyaniline was synthesized by subjecting an aqueous solution containing 1M aniline and 2M lithium perchlorate to constant potential electrolysis using a 20 mm x 22 mm platinum plate held at 0.8 V with respect to a saturated calomel electrode. The polyaniline adhered to the platinum plate was washed with water, dried, and then recovered as a powder. This polyaniline powder was vacuum dried at a temperature of 400° C. for 8 hours. 1 part by weight of polyethylene powder was mixed with 10 parts by weight of polyaniline powder, this mixed powder was filled into a foamable nickel plate, and the mixture was heated to 300 kg/cm' at a temperature of 120°C.
The positive electrode body of Example 2 was obtained by hot pressing at a pressure of .

Using the negative electrode body and positive electrode body obtained as above,
A battery shown in FIG. 4 was produced. In the figure, 11 is a negative electrode body,
12 is a positive electrode body, 13 is a polyethylene resin separator,
14 is an electrolytic solution made of propylene carbonate containing 1M lithium perchlorate as a solute; 15 is a battery container; 1
6.16' is the negative electrode Toden body, positive electrode current collector, 17.17'
are the negative terminal and the positive terminal.

When the charge/discharge capacities of the negative electrode and positive electrode were examined, they were each 5.0IIIAh. FIG. 5 shows the charging and discharging characteristics of these batteries when they were charged to 4V with a charging current of 1.25111A and discharged to OV with a discharge current of 1.25mA. FIG. 6 shows the cycle dependence of the discharge capacity when the above charge/discharge cycles were repeated. In the figure, A is for the battery of Example 1, and B is for Example 2.

In this way, the above-mentioned battery has the characteristics of a secondary battery that can be repeatedly charged and discharged, and has excellent cycle characteristics such that the dischargeable capacity does not decrease even after repeated charging and discharging under harsh conditions. Turns out it's a battery.

(G) Effects of the Invention The non-aqueous electrolyte secondary battery of the present invention has a high capacity and an excellent charge/discharge cycle life, and can withstand charging and discharging at a deep depth of charge.

Therefore, its industrial value is extremely large.

[Brief explanation of the drawing]

Fig. 1 relates to a manufacturing apparatus for a negative electrode body of a non-aqueous electrolyte secondary battery of the present invention, and Fig. 2 is an explanatory diagram of the configuration of a carbon body manufacturing apparatus used to explain the manufacture of a negative electrode body in Examples. FIG. 3 is an X-ray diffraction diagram of a carbon body according to an embodiment of the battery of the present invention. FIG. 4 is a Raman spectrum diagram of a carbon body according to an embodiment of the battery of the present invention. 5 is a charge/discharge characteristic diagram of an embodiment of the battery of the present invention, and FIG. 6 is a graph illustrating the relationship between the dischargeable capacity of the battery of the present invention and the number of repetitions of charge/discharge cycles. It is a diagram. 1... Bubble container, 2... Argon gas supply device, 3... Pyrex glass tube, 4...
Reaction tube, 5.6... Needle valve, 1... Sample holder, 8... Heating furnace, 9.10...
... Exhaust equipment, 11 ... Negative electrode body, 1
2... Positive electrode body, 13... Separator,
14... Electrolyte, 15... Battery container, 16.16'... Current collector, 17.17'
...Terminal. Figure 3□2 Unexamined Publication Day, ffG3-124380 (8) Figure 5 Figure 6

Claims (1)

[Claims] 1. A non-aqueous electrolyte secondary battery using a non-aqueous electrolyte containing a light metal such as lithium or sodium as an active material and disposing a negative electrode body and a positive electrode body through a separator. The electrode active material of the negative electrode body has an average interplanar spacing of 0.33.
7 to 0.355 nm, 1360c to 1580cm^-^1 in argon laser Raman spectrum
A carbon-based active material whose main component is a carbon body having a planar network six-membered ring structure with a Raman intensity ratio of 0.4 to 1.0 and selective orientation is used, and the positive electrode body is A non-aqueous electrolytic solution characterized by using an organic polymer active material whose main component is a conductive organic polymer capable of forming an electrochemically reversible charge transfer complex with an electron-accepting substance as an electrode active material. Secondary battery.