Process for producing an electrode material for a rechargeable lithium battery, an electrode structural body for a rechargeable lithium battery, process for producing said electrode structural body, a rechargeable lithium battery in which said electrode structural body is used, and a process for producing said rechargeable lithium battery

Abstract

A process for producing an electrode material for a rechargeable lithium battery, comprising the steps of mixing a metal compound (a) of a metal (a′) capable of being electrochemically alloyed with lithium, a transition metal compound (b) of a transition metal (b′) and a complexing agent (c) with a solvent (d) to obtain a mixed solution, mixing a reducing agent (e) with said mixed solution to obtain a mixture, and oxidizing said reducing agent in said mixture to reduce ion of said metal (a′) and ion of said transition metal (b′) to obtain an amorphous alloy material capable of being electrochemically alloyed with lithium as said electrode material. An electrode structural body in which said electrode material is used, and a rechargeable lithium battery in which said electrode material is used.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a process for producing an electrode material which can be desirably used in the production of a rechargeable lithium battery in which oxidation-reduction reaction of lithium (comprising oxidation reaction of lithium and reduction reaction of lithium ion) is used (this battery will be hereinafter referred to as rechargeable lithium battery for simplification purpose), an electrode structural body using said electrode material, a rechargeable lithium battery whose electrode comprising said electrode structural body, a process for producing said electrode structural body, and a process for producing said rechargeable lithium battery. More particularly, the present invention relates to an electrode structural body for a rechargeable lithium battery, which is constituted by an electrode material comprising a specific amorphous alloy material capable of being alloyed with lithium and whic...

AI Technical Summary

Benefits of technology

The present invention provides a process for producing an electrode material using a specific amorphous alloy material that can be electrochemically alloyed with lithium, which is suitable for use in rechargeable lithium batteries. The process involves mixing metal compounds, transition metal compounds, and a complexing agent in a solvent to obtain a mixed solution, adding a reducing agent to obtain a mixture, and oxidizing the reducing agent to deposit the amorphous alloy material. The resulting amorphous alloy material has excellent characteristics and is highly suitable for use as an electrode material in rechargeable lithium batteries. The invention also provides an electrode structural body comprising the electrode material, which has a high capacity and a prolonged cycle life, and a rechargeable lithium battery comprising the electrode structural body, which has a prolonged charging and discharging cycle life and a high energy density.

Problems solved by technology

Because of this, in such lithium ion battery, when the amount of lithium intercalated by the anode comprising the carbonous material (the graphite) is made greater than the theoretical amount upon performing charging operation or when charging operation is performed under condition of high electric current density, there will be an unavoidable problem such that lithium is deposited in a dendritic state (that is, in the form of a dendrite) on the surface of the anode.

This will result in causing internal-shorts between the anode and the cathode upon repeating the charging and discharging cycle.

Therefore, it is difficult for the lithium ion battery whose anode comprising the carbonous material (the graphite) to achieve a sufficient charging and discharging cycle life.

In addition, using this battery design, it is extremely difficult to attain a desirable rechargeable battery having a high energy density comparable to that of a primary lithium battery in which a metallic lithium is used as the anode active material.

However, such rechargeable battery is not practically usable one because its charging and discharging cycle life is extremely short.

The metallic lithium as the anode reacts with impurities such as moisture 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.

This situation often 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.

Thus, the growth of the lithium dendrite tends to cause internal-shorts between the anode and the cathode whereby occurring such problems as above described, where the battery is damaged or / and the lifetime of the battery is shortened.

However, this method is not widely applicable in practice for the following reasons.

The lithium alloy is hard and is difficult to wind into a spiral form and therefore, it is difficult to produce a spiral-wound cylindrical rechargeable battery.

Accordingly, it is difficult to attain a rechargeable battery having a sufficiently long charging and discharging cycle life.

It is also difficult to attain a rechargeable battery having a desirable energy density similar to that of a primary battery in which a metallic lithium is used as the anode.

By the way, when any of the foregoing 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 the anode active material, the specific surface area of a portion in the anode's electrode material layer contributing to the battery reaction is relatively small and therefore, the charging and discharging cycle is difficult to be effectively repeated with a large electric current.

Further, for a rechargeable battery in which any of the foregoing alloy materials is used the anode, there are such problems as will be described in the following.

Because of this, the anode has a tendency that it is eventually distorted and cracked.

In the case where the anode becomes to be in such state, when the charging and discharging cycle is repeated over a long period of time, in the worst case, the anode is converted into a pulverized state to have an increased impedance, resulting in shortening the charging and discharging cycle life.

Hence, none of the rechargeable batteries disclosed in the above-mentioned Japanese publications has been put to practical use.

In addition, the foregoing electrodes are those prepared by depositing such grained material as above described on the collector comprising a copper wire having a diameter of 0.07 and therefore, any of them is not of a practically usable electrode form.

However, for this electrode, the lifetime as a battery will be extremely shortened.

However, any of the anodes described in the above-mentioned publications is not decisive one which can markedly prolong the charging and discharging cycle life of the rechargeable lithium battery.

However, according to the technique described in this publication, it is difficult to realize a practically usable rechargeable lithium battery having a high capacity and a charging and discharging cycle life which falls in a practically usable region.

However, it is extremely difficult to industrially produce such low crystalline or amorphous intermetallic compound in practice.

According to the technique described in this publication, it is difficult to realize a practically usable rechargeable lithium battery having a high capacity and a prolonged charging and discharging cycle life.

However, this amorphous Co—Ni alloy cannot be used as the electrode material in a rechargeable lithium battery because it does not contain a metal capable of being alloyed with lithium.

As a result, it was found that any of the rechargeable lithium batteries does not have a charging and discharging cycle life which falls in a practically usable region.

Thus, according to the technique described in this document, it is difficult to realize a rechargeable lithium battery having a charging and discharging cycle life which falls in a practically usable region.

However, in this document, neither detailed description nor discussion are made of amorphilization for the conductive material constituting the electrode of the rechargeable battery.

Thus, it is difficult to recognize that the rechargeable battery disclosed in this document is satisfactory in terms of the charging and discharging cycle life.

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