JP2955192B2 - Electrodes for organic electrolyte batteries - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode for an organic electrolyte battery, and more particularly to an electrode for an organic electrolyte battery using the above-mentioned specific insoluble and infusible substrate as an electrode active material.

[0002]

2. Description of the Related Art In recent years, a secondary battery using a conductive polymer, a transition metal oxide or the like as a positive electrode and a lithium metal or a lithium alloy as a negative electrode has a high energy density.
It has been proposed as a battery replacing i-Cd batteries and lead batteries. However, when these secondary batteries are repeatedly charged and discharged, the capacity is greatly reduced due to deterioration of the positive electrode or the negative electrode, and there remains a practical problem. In particular, the deterioration of the negative electrode involves the formation of moss-like lithium crystals called dentite, and the repetition of charging and discharging eventually causes the dentite to penetrate the separator, causing a short circuit inside the battery, and in some cases, the battery exploding There was also a problem in terms of safety. In recent years, research on lithium batteries in which lithium is supported on a carbon material such as graphite, or a conductive polymer such as polyacetylene or polyparaphenylene has been advanced. However, when lithium is supported on a carbon material, for example, although the generation of dendrites is remarkably small, its utilization is about 16.7% in terms of mole percentage with respect to C ₆ Li, that is, carbon atoms. Further, when a carbon material is used for the negative electrode, there is a problem that the cycle characteristics are deteriorated due to a change in the structure when lithium is introduced or taken out.

On the other hand, Japanese Unexamined Patent Publication Nos. Hei 1-44422 and Hei 3-24024 disclose an insoluble infusible substrate (polyacene organic semiconductor) having a polyacene skeleton structure. The polyacene-based organic semiconductor is an amorphous organic semiconductor in which polycyclic aromatic hydrocarbons are appropriately developed, and is known to be a negative electrode active material of the above-described battery because it can dope, that is, carry lithium.
Generally, from the viewpoints of productivity, dimensional stability, and the like, a battery electrode obtained by adding a binder to an electrode active material powder and molding the same is preferably used. However, when the insoluble and infusible substrate is formed into an electrode, an unsatisfactory capacity remains. Further, Japanese Unexamined Patent Application Publication No.
JP-A-233860 describes an organic electrolyte battery in which an electrode comprising the insoluble and infusible substrate and a thermosetting resin is used as a negative electrode. In the battery, a battery excellent in cycle characteristics and rapid charge / discharge characteristics can be obtained by suppressing the loosening of the electrode when lithium is doped, but the capacity was still insufficient.

[0004]

In view of the above problems, the present inventors have made intensive studies and completed the present invention. An object of the present invention is to provide an electrode for an organic electrolyte secondary battery which has a high capacity and a high voltage, can be charged and discharged for a long time, and has a small decrease in capacity. Still another object of the present invention is to provide an electrode for a secondary battery having excellent safety. Still another object of the present invention is to provide an electrode for a secondary battery which is easy to manufacture. Still other objects and advantages of the present invention will become apparent from the following description.

[0005]

Means for Solving the Problems The present inventors have completed the present invention by using an insoluble and infusible substrate having a polyacene skeleton structure having a specific pore structure as an electrode active material. That is, the present invention relates to a heat-treated aromatic condensed polymer, and an insoluble and infusible substrate having a polyacene skeleton structure having a hydrogen atom / carbon atom ratio (H / C) of 0.5 to 0.05. An electrode for an organic electrolyte battery, characterized in that a material having an adsorbed gas amount of 100 cc / g or less at a nitrogen adsorption thickness of 10 ° obtained from a nitrogen adsorption isotherm of the insoluble infusible substrate is used as an electrode active material. It is.

The aromatic condensation polymer in the present invention is a condensation product of an aromatic hydrocarbon compound having a phenolic hydroxyl group with an aldehyde. As the aromatic hydrocarbon compound, for example, so-called phenols such as phenol, cresol, and xylenol are suitable, but not limited thereto. For example,

Embedded image (Where x and y are each independently 0, 1 or 2
Methylene bisphenols represented by the formula: or hydroxy biphenyls or hydroxynaphthalenes. Of these, phenols, particularly phenol, are practically preferred.
In particular, as the aromatic condensation polymer in the present invention,
A modified aromatic condensation polymer in which a part of the aromatic hydrocarbon compound having a phenolic hydroxyl group is substituted with an aromatic hydrocarbon compound having no phenolic hydroxyl group, such as xylene, toluene, or aniline, such as phenol A condensate of xylene and formaldehyde is preferably used. Modified aromatic polymers substituted with melamine or urea or furan resins can also be used. Aldehydes such as formaldehyde, acetaldehyde and furfural can be used, but formaldehyde is preferred. The phenol formaldehyde condensate may be any of a novolak type, a resol type, or a mixture thereof.

The insoluble and infusible substrate of the present invention can be obtained by heat-treating the above aromatic polymer.
Any insoluble and infusible substrate having a polyacene-based skeleton structure described in JP-A-44212 can be used, and for example, it can also be produced as follows. The aromatic condensation polymer is gradually heated to a suitable temperature of 400 ° C. to 800 ° C. in a non-oxidizing atmosphere (including a vacuum) to obtain an atomic ratio of hydrogen atoms / carbon atoms (hereinafter H). / C) of 0.50 to 0.05, preferably 0.35 to 0.10.

The insoluble infusible substrate used in the present invention has a main peak at 2θ according to X-ray diffraction (CuKα).
And there are other broad peaks between 41 and 46 ° in addition to the main peak. That is, it is suggested that the insoluble infusible substrate has a polyacene skeleton structure in which an aromatic polycyclic structure is appropriately developed and has an amorphous structure, and is useful as an active material for a battery because lithium can be stably doped. It is. When H / C exceeds 0.50, doping of lithium,
Dedoping cannot be performed smoothly, and when a battery is assembled, the charge / discharge efficiency decreases. In addition, H / C is 0.0
If it is 5 or less, the capacity of the battery using the electrode of the present invention is undesirably reduced. The shape of the insoluble and infusible substrate used in the present invention is not particularly limited as long as it can be molded, such as powder, short fiber, or the like.
The following powders are preferred.

The electrode of the present invention is formed by adding the above-mentioned insoluble and infusible substrate and, if necessary, a conductive material and a binder, and the type and composition of the conductive material and the binder are not particularly limited. . The type of the conductive material is not particularly limited, and a metal powder such as metallic nickel may be used, but a carbon-based material such as activated carbon, carbon black, acetylene black, and graphite is particularly preferable. The mixing ratio varies depending on the conductivity of the insoluble infusible substrate and the shape of the electrode, but it is appropriate to add 2 to 40% to the insoluble infusible substrate. Although the kind of the binder is not particularly limited, for example, SBR
Such as rubber-based binder, polytetrafluoroethylene, fluorine-containing resin such as polyvinylidene fluoride, polypropylene,
A thermoplastic resin such as polyethylene is preferable, and the mixing ratio is preferably 20% or less. The shape of the electrode of the present invention can take various shapes, such as a plate shape, a film shape, a column shape, or a shape formed on a metal foil, depending on a target battery. In particular, those formed on a metal foil are preferable because they can be applied to various batteries as a current collector integrated electrode. In the electrode of the present invention, by using PAS having a specific pore structure as an electrode active material, the capacity of a battery using the electrode can be significantly improved as compared with a conventional battery. The amount of nitrogen gas adsorbed on the PAS in the present invention was measured as follows. That is, 0.035 g of PAS powder having an average particle size of 15 μm pulverized by a disk mill was put into a sample cell of a constant volume apparatus (Autosorb-1 manufactured by Yuasa Ionics), and nitrogen gas was adsorbed at a liquid nitrogen temperature of 77 ° K. Was. From the obtained adsorption isotherm, the adsorption gas amount (cc / g) was plotted against the adsorption gas layer thickness t (Å). The following equation was used as t (Å).

(Equation 1) (Where P / P ₀ is the relative pressure of nitrogen gas) In the present invention, the amount of gas adsorbed on the PAS at a nitrogen adsorption thickness of 10 ° is 100 cc / g or less, preferably 80 cc / g or less, and more than 100 cc / g. Not enough capacity is obtained.

The electrode for an organic electrolyte battery according to the present invention, in which the PAS having the above specific pore structure is used as an electrode active material, is a high capacity and high voltage electrode for an organic electrolyte secondary battery.

Hereinafter, the present invention will be described specifically with reference to examples.

Example 1 A xylene-modified novolak resin was obtained by heating 50 parts by weight of a xylene resin (manufactured by Lignite), 50 parts by weight of novolak (manufactured by Showa Polymer Co., Ltd.), and 0.1 part by weight of xylene sulfonic acid at 100 ° C. Was. 10 parts by weight of hexamethylenetetramine was mixed with 100 parts by weight of the resin, and the mixture was pulverized and formed into a molded plate by hot pressing. The xylene-modified novolak resin molded plate was placed in a siliconite electric furnace and heated at a rate of 10 ° C./hour under a nitrogen atmosphere at 650 ° C.
To form an insoluble infusible substrate (referred to as PAS). The PAS plate thus obtained was pulverized with a disk mill to obtain a PAS powder having an average particle size of 15 μm.
The H / C ratio was 0.22. The amount of gas adsorbed on the PAS powder at a nitrogen adsorption thickness of 10 ° was 29 cc / g. Next, 100 parts by weight of the PAS powder and 100 parts by weight of a solution obtained by dissolving 10 parts by weight of polyvinylidene fluoride powder in 90 parts by weight of N, N-dimethylformamide were sufficiently mixed to obtain a slurry. The slurry was applied on a 10 μm thick copper foil (negative electrode current collector) using an applicator, dried and pressed to obtain a 110 μm thick PAS negative electrode. To 100 parts by weight of commercially available LiCoO ₂ (manufactured by Strem), 5 parts by weight of polytetrafluoroethylene and 10 parts by weight of acetylene black were mixed well, and a positive electrode sheet having a thickness of 700 μm was obtained using a roller.

Using the above positive and negative electrodes (1 × 1 cm ² ), FIG.
A battery like that was assembled. A stainless steel mesh was used as the positive and negative electrode current collectors, and a felt made of glass fiber was used as the separator. As the electrolyte, propylene carbonate and diethyl carbonate in a ratio of 1: 1 (weight ratio)
A solution in which LiPF ₆ was dissolved at a concentration of 1 mol / l was used for the mixed solution. At a rate at which lithium doping of the battery is 1% / hour in mole percentage with respect to the PAS of the negative electrode,
That is, constant current charging is performed with the current calculated by the following equation, and charging is performed until the voltage at the time of energization becomes 3.9 V.
Lithium was supported on the negative electrode PAS.

(Equation 2) Subsequently, constant current discharging was performed with the same current as charging, and discharging was performed until the open-circuit voltage (measured at the battery voltage when left for 1 hour after opening the charging circuit) reached 3.0 V. The battery capacity was evaluated at the third discharge capacity value by repeating the above charging and discharging. The third discharge capacity was 5.2 mAh. Here, the PAS utilization rate can be calculated by the following equation, and the amount of lithium undoped from the PAS of the negative electrode is expressed by PAS
Is a numerical value expressed as a percentage of carbon atoms, and in the case of Example 1, the PAS utilization was 23.7%.

(Equation 3)

Example 2 The molded sheet of xylene-modified novolak resin of Example 1 was placed in a siliconite electric furnace under a nitrogen atmosphere.
The temperature was raised at a rate of ° C./hour, and the plate obtained by heat-treating to 600 ° C. and 700 ° C. was pulverized with a disk mill to obtain an average particle size of 15 μm, an H / C ratio of 0.30,
PAS powders having an adsorption gas amount of 24 cc / g and 32 cc / g at a nitrogen adsorption thickness of 10 mm and 0.17, respectively were obtained. Next, an electrode was formed in the same manner as in Example 1. Further, using the same positive electrode as in Example 1, a battery similar to that of Example 1 was assembled, and the third capacity was evaluated in the same manner. As a result, the capacity was 5.1 mAh and 5.0 mAh, respectively.

Example 3 In Example 1, the composition of the PAS raw material was changed to 30 parts by weight of xylene resin, 70 parts by weight of novolak, and 10 parts by weight of xylene resin, 90 parts by weight of novolak, and the xylene-modified novolak resin was molded in the same manner as in Example 1. A plate was obtained and heat-treated and pulverized in the same manner as in Example 1 to obtain PAS.
It was a powder. The average particle size of the PAS powder is 15 μm, H /
The C ratio was 0.22 and 0.23, respectively. The adsorbed gas amounts of the PAS powder at a nitrogen adsorption thickness of 10 ° were 60 cc / g and 83 cc / g, respectively. Next, an electrode was formed in the same manner as in Example 1. Further, using the same positive electrode as in Example 1, a battery similar to that of Example 1 was assembled, and the capacity was evaluated for the third time.
Ah and 4.6 mAh.

[0012]

Comparative Example 1 A phenolic resin molded plate was obtained in the same manner as in Example 1 except that the composition of the PAS raw material was 100 parts by weight of novolak, 10 parts by weight of hexamethylenetetramine, and powdered resole (manufactured by Showa Polymer). Further, heat treatment and pulverization were performed in the same manner as in Example 1 to obtain PAS powder. The PAS powder had an average particle size of 15 μm and an H / C ratio of 0.21, 0.
23, the nitrogen adsorption amounts at a nitrogen adsorption thickness of 10 ° were 120 cc / g and 132 cc / g, respectively. Next,
An electrode was formed in the same manner as in Example 1. Further, the same battery as in Example 1 was assembled using the same electrodes as in Example 1, and the third capacity was evaluated in the same manner.
And 4.0 mAh.

Comparative Example 2 In Example 1, a commercially available graphite powder (manufactured by Lonza, having an average particle size of 15 μm) was used in place of the PAS powder.
m) was used as an electrode in the same manner as in Example 1. Further, the same positive electrode as in Example 1 was used, a battery similar to that in Example 1 was assembled, and the third capacity was evaluated in the same manner.
mAh. The above results are summarized in the table.

[Table 1] As is clear from the examples and comparative examples, the electrode for an organic electrolyte battery of the present invention uses an insoluble and infusible substrate having a polyacene-based skeleton structure having a specific pore structure as an active material. The capacity of the battery created by the above is dramatically improved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a basic configuration of a battery according to the present invention.

[Description of Signs] 1 Positive electrode 2 Negative electrode 3 3 'current collector 4 Electrolyte 5 Separator 6 Battery case 7 7' External terminal

──────────────────────────────────────────────────続 き Continued on the front page Examiner Yoshihisa Ishii (58) Field surveyed (Int.Cl. ⁶ , DB name) H01M 4/02 H01M 4/58 H01M 10/40

Claims (1)

(57) [Claims] 1. A heat-treated aromatic condensation polymer having a hydrogen atom / carbon atom ratio (H / C) of from 0.5 to 0.5.
An insoluble infusible substrate having a polyacene-based skeletal structure of 0.05 and having an adsorbed gas amount of 100 cc / g or less at a nitrogen adsorption thickness of 10 ° obtained from a nitrogen adsorption isotherm of the insoluble infusible substrate. An electrode for an organic electrolyte battery, characterized by using as an electrode active material.