JP2853707B2 - Button type organic electrolyte secondary battery - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chargeable / dischargeable button-type organic electrolyte secondary battery expected to be used as a power source for various small electronic devices. 2. Description of the Related Art A so-called organic electrolyte battery using lithium as a cathode material and an organic electrolyte as an electrolyte has a low self-discharge, a high voltage, and extremely excellent preservability. It has been widely used as a battery having a long-term reliability of 10 to 10 years as an electronic timepiece, a power supply for various memory backups, and the like. [0003] However, these currently used organic electrolyte batteries are primary batteries, and the life thereof ends after a single use, so that there is a need to improve the economy. In recent years, with the rapid progress of various electronic devices, there has been a strong demand for a rechargeable organic electrolyte secondary battery as a power source that can be used conveniently and economically for a long time. Is underway. In general, as a cathode material of an organic electrolyte secondary battery, metallic lithium, lithium alloy (for example, Li-Al
Alloys), conductive polymers doped with lithium ions (for example, polyacetylene or polypyrrole), and intercalation compounds in which lithium ions are mixed in crystals are used. Organic electrolytes are used as electrolytes. . [0006] On the other hand, various materials have been proposed and researched as anode active materials. Typical examples thereof include TiS ₂ , as described in JP-A-50-54836.
MoS ₂ , NbSe ₂ , V ₂ O _{5 and the} like. The discharge reaction of a battery using these materials proceeds by intercalating lithium ions of the cathode between layers of these materials which are the anode active material,
Conversely, when charging, lithium ions deintercalate from the layers of the material to the cathode. That is,
Charge and discharge can be repeated by repeating a reaction in which lithium ions of the cathode enter and exit between layers of the anode active material. For example, when TiS ₂ is used as the anode active material, the charge and discharge reactions are represented by the following equations. [0008] [0009] The charge and discharge of the conventional anode material proceed by the above-described reaction, but there is a disadvantage that the discharge capacity gradually decreases as the charge and discharge reaction is repeated as a secondary battery. This is because the lithium ions that have entered the anode active material due to the discharge gradually become difficult to go outside, and the amount that returns to the cathode side by the charge reaction decreases. That is, since the anode remains in the form of Li _x TiS ₂ , the amount of lithium ions involved in the next discharge reaction decreases. Therefore, even if the battery is charged, the secondary battery has a reduced discharge capacity and poor cycle life characteristics. [0010] As described above, in the materials used as the anode active material of the conventional secondary battery,
The charge reaction does not proceed as expected, the discharge capacity decreases as charging and discharging are repeated, the cycle life characteristics are not excellent,
It was a secondary battery that could not be used for a long time. In view of the above, the present invention has been proposed in view of the above-mentioned conventional circumstances, and uses a material having a small deterioration of lithium ion deintercalation found in a conventional anode active material, and performs charge and discharge. An object of the present invention is to provide a button-type organic electrolyte secondary battery that has less deterioration in discharge capacity due to cycling and has excellent cycle life characteristics. Means for Solving the Problems The present inventor has conducted various studies in order to find a material with less deterioration of lithium ion deintercalation as an anode active material in order to achieve the above object. , LiMn with spinel structure
_{It has been found that 2} O ₄ shows extremely good results. The button-type organic electrolyte secondary battery according to the present invention has been completed based on such knowledge, and a cathode pellet containing lithium and an anode pellet containing LiMn ₂ O ₄ as an anode active material are overlapped via a separator. The separator is housed together with the organic electrolytic solution in the cathode can and the anode can which are caulked via a gasket, and the peripheral portion of the separator is sandwiched between the cathode can and the gasket, and between the gasket and the separator. Is characterized in that a space portion is formed. [0013] The button-type organic electrolyte secondary battery according to the present invention having the above-described structure has LiMn as an anode active material.
By using ₂ O ₄ , lithium ions of the cathode material moved to the anode by the discharge reaction can be favorably deintercalated in the reaction by the charge. Further, in the button-type organic electrolyte secondary battery according to the present invention, the repetitive charge / discharge causes a significant change in the volume of LiMn ₂ O _{4 as} the anode active material. In this button-type electrolyte secondary battery, a space is formed between the gasket and the separator.
It can exhibit a buffering action against a rapid rise in internal pressure due to a volume change of n ₂ O ₄ . DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the button-type organic electrolyte secondary battery according to the present invention will be described below in detail with reference to the drawings. However, the present invention is not limited to these experimental examples. Not to mention that it is not. LiMn ₂ O ₄ used as the anode active material of the button type organic electrolyte secondary battery of the present invention is obtained by heating lithium carbonate (Li ₂ Co ₃ ) and manganese dioxide (MnO ₂ ) to 400 ° C. in a nitrogen atmosphere. Or can be easily obtained by reacting lithium iodide (LiI) and manganese dioxide (MnO ₂ ) by heating to 300 ° C. in a nitrogen atmosphere. On the other hand, lithium-containing substances used as cathode materials include metallic lithium and lithium alloys (eg, LiAl, LiPb, LiSn, LiBi,
LiCd, etc.), conductive polymers doped with lithium ions (eg, polyacetylene, polypyrrole, etc.),
Interlayer compounds in which lithium ions are mixed in the crystal (for example, those containing lithium between layers of TiS ₂ , MoS ₂ , etc.) can be used. As the electrolyte, a non-aqueous organic electrolyte obtained by dissolving a lithium salt in an organic solvent is used. Here, as the organic solvent, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolan, 4-methyl-1,3
-A single solvent such as dioxolane or a mixture of two or more solvents can be used. As the electrolyte, LiClO ₄ , LiAs
One of F ₆ , LiPF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄
A species or a mixture of two or more species can be used. Hereinafter, Comparative Examples, Examples 1 and 2, which were actually manufactured by applying the present invention, will be described. Comparative Example First, cycle characteristics of a Li / TiS ₂ or Li / MoS ₂ organic electrolyte secondary battery using TiS ₂ or MoS ₂ as an anode active material were examined. The result is shown in FIG. According to FIG. 1, TiS ₂ or M
The organic electrolyte secondary battery using oS ₂ is decreased only by repeated charge and discharge cycles of about 10 times the battery discharge capacity rapidly, the discharge capacity of the organic electrolyte secondary battery had initially Only about half the capacity was discharged. Thereafter, it was found that the discharge capacity decreased as the charge / discharge cycle was repeated. Example 1 A button type battery shown in FIG. 2 was manufactured according to the following procedure. After 87 g of commercially available electrolytic manganese dioxide and 26 g of lithium carbonate were sufficiently mixed in a mortar, this mixture was subjected to a heat treatment at 400 ° C. for 10 hours in an atmosphere of nitrogen gas on an alumina board. After cooling, the obtained product was analyzed by X-ray. As a result, an X-ray diffraction chart as shown in FIG. 3 was obtained.
When this was compared with a substance represented by the chemical formula LiMn ₂ O ₄ on an ASTM card, it completely matched the X-ray diffraction chart shown in LiMn ₂ O ₄ . Therefore, the substance generated by the above operation is LiMn ₂ O ₄ . Next, the LiMn obtained as described above is used.
8.9 parts by weight of graphite was added to 88.9 parts by weight of ₂ O ₄ , and 1.8 parts by weight of polytetrafluoroethylene was further added as a binder, and the diameter of the mixture was reduced to 1 ton / cm ^{2 at} a pressure of 3 tons / cm ^2.
A pellet having a thickness of 5.5 mm and a thickness of 0.3 mm was formed. This was further vacuum-dried at 300 ° C. for 5 hours to obtain an anode pellet (5). On the other hand, an aluminum foil having a thickness of 0.3 mm
Punched to 5.5 mm, spot-welded to the cathode can (2), and placed a 0.3 mm thick lithium foil on the
m was pressed to obtain a cathode as a cathode pellet (1). Next, a non-woven fabric of propylene is laminated on the cathode as a separator (3), and 1 mol / l of LiClO
A propylene carbonate in which ₄ was dissolved was added as an electrolytic solution, and a plastic gasket (4) was inserted. The anode pellet (5) already prepared was stacked on the separator (3), and the anode can (6) was covered. Thereafter, the opening is sealed by caulking so as to seal, and the outer diameter is 20.0 mm.
An organic electrolyte secondary battery having a thickness of 1.6 mm and a thickness of 1.6 mm was produced. This battery was designated as sample battery A. Example 2 50 g of commercially available electrolytic manganese dioxide and 39 lithium iodide
g and graphite (5.2 g) were sufficiently mixed in a mortar, and the mixture was pressed into a pellet at a pressure of 3 ton / cm ² , and then pressed on an alumina board in a nitrogen gas atmosphere.
Heat treatment was performed at 0 ° C. for 6 hours. After cooling, it was washed with ethylene glycol dimethyl ether (DME). When the obtained product was analyzed by X-ray, an X-ray diffraction chart as shown in FIG. 4 was obtained. When this was compared with a substance represented by the chemical formula LiMn ₂ O ₄ in an ASTM card,
It almost coincided with the X-ray diffraction chart shown by Mn ₂ O ₄ . Therefore, the substance produced by the above operation is LiMn ₂ O ₄
It is. In addition, in FIG. 4, a generation peak of Li ₂ MnO ₃ was observed, although slightly, with a graphite peak. Next, the LiMn obtained as described above is used.
_A sample battery B was prepared in the same procedure as in Example 1 using ₂ O ₄ . The sample battery A manufactured as described above
When a discharge test was performed on the sample battery B via a 1 kΩ resistor, the discharge electrode wire shown in FIG. 5 was obtained. The capacity obtained by this discharge was in excellent agreement with the capacity obtained by the following reaction formula. Li ⁺ + LiMn ₂ O ₄ → 2LiMnO ₂ Subsequently, the discharged sample battery A and sample battery B were charged at a current of 2 mA at an upper limit voltage of 3.1 V. FIG. 6 shows the result. According to FIG. 6, it can be seen that the charging voltage is extremely flat, which is considered to mean that deintercalation of lithium ions in the charging reaction represented by the following equation has evolved extremely smoothly. 2LiMnO ₂ → LiMn ₂ O ₄ + Li ⁺ Charge / discharge was repeated using the sample batteries A and B exhibiting the above charge / discharge characteristics. When the charge / discharge cycle characteristics of the sample battery were examined, as shown in FIG. 7, no deterioration of the discharge capacity due to the charge / discharge cycle was observed at all, and it was found that a very excellent secondary battery was obtained. . In addition, in the button-type organic electrolyte secondary battery according to the present invention shown in FIG. 2, the volume of LiMn ₂ O _{4 as} the anode pellet (5) is greatly changed by repeated charging and discharging. In this button-type electrolyte secondary battery, since a space is formed between the gasket 4 and the separator 3, this space has a buffering action against a rapid increase in internal pressure due to a volume change of LiMn ₂ O _4. Can be shown. Therefore, the button-type organic electrolyte secondary battery has excellent durability. As is apparent from the above description, LiMn ₂ O _{4 is} used as the anode active material of the button-type organic electrolyte secondary battery.
By using, it becomes possible to favorably deintercalate the lithium ions moved to the anode by the discharge reaction in the reaction by charging, and the charge / discharge cycle life characteristics of the button-type organic electrolyte secondary battery are greatly improved. It is possible to Therefore, it is possible to provide a button-type organic electrolyte secondary battery which is less deteriorated in battery capacity due to charge / discharge cycles and has excellent cycle life characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a characteristic diagram showing charge / discharge cycle characteristics of a button-type organic electrolyte secondary battery using TiS ₂ and MoS ₂ as an anode agent. FIG. 2 is a schematic sectional view showing a configuration example of a button-type organic electrolyte secondary battery according to the present invention. FIG. 3 is a characteristic diagram showing an X-ray diffraction result of LiMn ₂ O ₄ synthesized from electrolytic manganese dioxide and lithium carbonate. FIG. 4 is a characteristic diagram showing an X-ray diffraction result of LiMn ₂ O ₄ synthesized from electrolytic manganese dioxide and lithium iodide. FIG. 5 is a characteristic diagram showing discharge characteristics of a button-type organic electrolyte secondary battery to which the present invention is applied. FIG. 6 is a characteristic diagram showing charging characteristics of a button-type organic electrolyte secondary battery to which the present invention is applied. FIG. 7 is a characteristic diagram showing charge / discharge cycle characteristics of a button-type organic electrolyte secondary battery to which the present invention is applied. [Brief description of reference numerals] 1 Cathode pellet, 2 Cathode can, 3 Separator, 4
Gasket, 5 anode pellets, 6 anode cans

Claims (1)

(57) [Claims] A cathode pellet containing lithium and an anode pellet containing LiMn ₂ O ₄ as an anode active material are superimposed via a separator, and housed together with an organic electrolyte in a cathode can and an anode can which are caulked via a gasket, A button-type organic electrolyte secondary battery, wherein a peripheral portion of the separator is sandwiched between the cathode can and the gasket, and a space is formed between the gasket and the separator.