Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Electrode
Reexamination Certificate
1998-01-28
2002-08-13
Kalafut, Stephen (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Electrode
C429S209000, C429S235000
Reexamination Certificate
active
06432585
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an improved electrode structural body and a rechargeable battery provided with said electrode structural body. More particularly, the present invention relates an improved electrode structural body having a specific electrode material layer and which is suitable for use, particularly in rechargeable batteries such as rechargeable lithium series batteries and rechargeable zinc series batteries (these rechargeable batteries will be hereinafter referred to simply as rechargeable battery) and a rechargeable battery provided with said electrode structural body and which is always highly safe and stably exhibits excellent battery performances while preventing the generation of growth of a dendrite of lithium or zinc upon the repetition of the charging and discharging cycle, and which has a prolonged cycle life (a prolonged charging and discharging cycle life).
The present invention also relates a process for the production of said electrode structure and a process for the production of said rechargeable battery.
2. Related Background Art
In recent years, increasing levels of atmospheric CO
2
has been predicted to cause increase in the earth's temperature, due to the green house effect.
In the case of the steam-power generation, increasing amounts of a fossil fuel represented by coal or petroleum are being consumed for power generation in order to comply with a societal demand for increased power supply. Along with this, the amount of exhaust Ones from the steam-power generation plants has also been continuously increased while accordingly increases the amount of greenhouse gases such as carbon dioxide gas in the air. This results in an earth-warming phenomenon. In order to prevent the earth-warming phenomenon from further developing, prohibitions on newly established steam-power generation plants have been implemented in some countries.
Under these circumstances, use of load leveling has been proposed in order to effectively utilize the power generator, where rechargeable batteries are installed in locations and a surplus power unused in the night, a so-called dump power, is stored in these rechargeable batteries, the power thus stored is supplied in the daytime when the power demand is increased, whereby the power generator is leveled in terms of the load therefor.
In recent years, electric vehicles which do not exhaust any air polluting substances such as COx, NOx, hydrocarbons, and the like and are of low impact to the environment have been developed. For such electric vehicle, there is an increased demand for developing a high performance rechargeable battery with a high energy density which can be effectively used therein.
On the other hand, there is also an increased demand for developing a miniature, lightweight, high performance rechargeable battery usable as a power source for potable instruments such as small personal computers, word processors, camcorders, and cellular phones.
As such rechargeable battery, there has proposed various rocking chair type lithium ion batteries in which a carbonous material such as graphite capable of intercalating lithium ion at intercalation sites of its six-membered network plane provided by carbon atoms in the battery reaction upon charging is used as an -anode material and a lithium intercalation compound capable of deintercalating said lithium ion from the intercalation in the battery reaction upon charging is used as a cathode material. Some of these lithium ion batteries hive been practically used. However, in any of these lithium ion batteries, the theoretical amount of lithium, which can be intercalated by the anodes is only an amount of ⅙ per carbon atom. Therefore, using this battery design, it is impossible to attain a desirable rechargeable battery having a high energy density comparable to that of a primary lithium battery in which metallic lithium is used as the anode active material.
Further, in such lithium ion battery, when the amount of lithium intercalated by the anode is made greater than the theoretical amount or charging is conducted under condition of high electric current density, there will an unavoidable problem such that lithium is deposited in a dendritic state (that is, in the form of a dendrite) on the anode comprising the carbonous material during the charging operation. This will result in causing internal-shorts between the anode and the cathode upon repeating the charging and discharging cycle, wherein there cannot attain a sufficient charging and discharging cycle life. in addition, it is difficult to operate charging with such high electric current density in the case of a rechargeable battery in which a conventional aqueous series electrolyte solution is used.
Now, rechargeable lithium batteries in which a metallic lithium is used as the anode have been proposed and they have attracted public attention in a viewpoint that they exhibit a high energy density. However, such rechargeable battery is not practically usable one because its charging and discharging cycle life is extremely short. A main reason for this has been generally considered as will be described in the following. The metallic lithium as the anode reacts with impurities such as water or an organic solvent contained in an electrolyte solution to form an insulating film or/and the metallic lithium as the anode has an irregular surface with portions. to which electric field is converged, and these factors lead to generating a dendrite of lithium upon repeating the charging and discharging cycle, resulting in internal-shorts between the anode and cathode. As a result, the charging and discharging cycle life of the rechargeable battery is extremely shortened.
When the lithium dendrite is formed to make the anode and cathode such that they are internally shorted with the cathode, the energy possessed by the battery is rapidly consumed at the internally shorted portion. This creates problems in that the battery is heated or the solvent of the electrolyte is decomposed by virtue of heat to generate gas, resulting in an increase in the inner pressure of the battery. These problems result in damaging the rechargeable battery or/and shortening the lifetime of the battery.
Use of a lithium alloy such as lithium-aluminum alloy as the anode for a rechargeable lithium battery has been proposed as a way to suppress the reactivity of the lithium with water or an organic solvent contained in the electrolyte solution to prevent lithium dendrite formation. However, this is not practical for the following reasons. The lithium alloy is difficult to fabricate into a spiral form and therefore, it Is difficult to produce a spiral-wound cylindrical rechargeable battery. Accordingly, it is difficult to attain a desirable charging and discharging cycle life for a rechargeable battery obtained, and the rechargeable battery, it is difficult attain a: desirable energy density similar to that of a primary battery in which a metallic lithium is used as the anode.
Japanese Unexamined Patent Publications Nos. 64239/1996, 62464/1991, 12768/1990, 113366/1987, 15761/1987, 93866/1987, and 78434/1979 disclose various metals, i.e., Al, Cd, In, Sn, Sb, PC and Bi as the metal capable of forming an alloy with lithium in a rechargeable battery when the battery is subjected to charging, and rechargeable batteries in which these metals, alloys of these metals, or alloys of these metals with lithium are used as the anodes.
However, these documents do not detail about the configurations of the anodes. And any of the rechargeable batteries disclosed in these documents is problematic in that when any of the alloy materials is fabricated into a plate-like form, such as a foil form which is generally adopted as an electrode of a rechargeable battery and it is used as an anode of a rechargeable battery in which lithium is used as an active material, the surface area of a portion contributing to the battery reaction in the electrode material layer is relatively small and therefore, the charging a
Asao Masaya
Kawakami Soichiro
Kimura Hironao
Kobayashi Naoya
Kosuzu Takeshi
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Ruthkosky Mark
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