Non-aqueous electrolyte cell

Details Non-aqueous electrolyte cell Non-aqueous electrolyte cell

1999-11-23

2001-09-18

Kalafut, Stephen (Department: 1745)

Chemistry: electrical current producing apparatus, product, and

Current producing cell, elements, subcombinations and...

Include electrolyte chemically specified and method

C429S218100, C429S224000

Reexamination Certificate

active

06291108

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a non-aqueous electrolyte cell comprising a positive electrode, a negative electrode and a non-aqueous electrolyte consisting of a solute and an organic solvent.
2. Description of the Prior Art
A non-aqueous electrolyte cell in which a negative electrode has lithium or a lithium alloy as an active material provides the advantages of high energy density and low self-discharge rate.
In this type of cell, a low boiling point solvent such as dimethoxyethane or dioxolane has been conventionally used as a solvent of an electrolyte. However, the solvent reacts with lithium, whereby a film, which is inactive and has a low conductivity, is formed on surfaces of the negative electrode. This causes the internal resistance of the cell to be increased, resulting in deterioration of storage characteristics (especially, a high rate discharge characteristic after storage).
In order to solve the above problem, it has been proposed to employ a solvent mixture of a cyclic carbonate and a low boiling point solvent to form a film of Li
2
CO
3
, which has a high conductivity on surfaces of the negative electrode, thereby improving the storage characteristics. However, this does not provide satisfactory storage characteristics.
OBJECTS AND SUMMARY OF THE INVENTION
An object of the present invention, therefore, is to provide a non-aqueous electrolyte cell capable of drastically improving a high rate discharge characteristic after storage as well as before storage.
Another object of the present invention is to provide a non-aqueous electrolyte cell capable of improving a charge and discharge cycle characteristic before and after storage when used as a secondary cell.
The above objects are fulfilled by a non-aqueous electrolyte cell comprising a positive electrode, a negative electrode, and an electrolyte consisting of a solute and an organic solvent, the cell being characterized in that the solvent is a solvent mixture of a cyclic carbonate and a non-cyclic carbonate.
The above objects are also fulfilled by a dischargeable non-aqueous electrolyte primary cell comprising a positive electrode; a negative electrode including either one of lithium and a lithium alloy; and a non-aqueous electrolyte consisting of a solute and an organic solvent, wherein the organic solvent is a solvent mixture of a cyclic carbonate and a non-cyclic carbonate.
The above objects are also fulfilled by a rechargeable non-aqueous electrolyte secondary cell comprising a positive electrode having a rechargeable substance as an active material; a negative electrode having lithium or a lithium alloy as an active material; and a non-aqueous electrolyte consisting of a solute and an organic solvent, wherein the organic solvent is a solvent mixture of a cyclic carbonate and a non-cyclic carbonate.
The above objects are fulfilled for the following reasons:
A storage characteristic in a non-aqueous electrolyte cell is deteriorated since a film having a low conductivity is generated by reaction between lithium and a solvent during long-term storage. When the solvent comprises a cyclic carbonate such as propylene carbonate or ethylene carbonate, a film of Li
2
CO
3
, which does not increase the internal resistance of the cell, is formed on the negative electrode, whereby the storage characteristic can be improved.
However, if the solvent consists of a cyclic carbonate only, the high rate discharge characteristic is deteriorated due to high viscosity of the electrolyte. Therefore, a solvent mixture of a cyclic carbonate and a low boiling point solvent having a low viscosity such as dimethoxyethane or dioxolane is generally used. However, such a solvent mixture also has the problem that reaction between lithium and the low boiling point solvent is inevitable after long term storage, although the high rate discharge characteristic is improved. The reaction forms an inactive film of Li
2
O, whereby the high rate discharge characteristic is deteriorated after long term storage.
In order to solve the above problems, the present invention employs a solvent mixture of a cyclic carbonate and a non-cyclic carbonate having a low viscosity. In this case, the viscosity of the electrolyte becomes lower than that of the cyclic carbonate solvent, whereby the high rate discharge characteristic is improved. Moreover, since each carbonate forms a film of Li
2
CO
3
, the post-storage high rate discharge characteristic is further improved.
When the present invention is applied to a secondary cell the storage characteristic and the charge and discharge cycle characteristic are improved because of the formation of the film having a high conductivity.


REFERENCES:
patent: 4048403 (1977-09-01), Kronenberg
patent: 4056663 (1977-11-01), Schlaikjer
patent: 4615959 (1986-10-01), Hayashi et al.
patent: 4957833 (1990-09-01), Daifuku
patent: 5256504 (1993-10-01), Okuno et al.
patent: 5270134 (1993-12-01), Tobishima et al.
patent: 5523443 (1996-06-01), Okuno et al.
patent: 2016777 (1990-11-01), None
patent: 2118400 (1993-03-01), None
patent: 0312236 (1988-05-01), None
patent: 2641130 (1989-12-01), None
patent: 61-64082 (1986-04-01), None
patent: 2-010666 (1990-01-01), None
patent: 2-267871 (1990-02-01), None
Patent Abstracts of Japan, vol. 14, No. 154 (E-907) [4097] Corresponding to Japanese 2-12777, Mar. 23, 1990.*
Patent Abstracts of Japan, JP2010666, Non-Aqueous Electrolyte Secondary Battery.

Affiliated with

Also associated with

Rating

Non-aqueous electrolyte cell does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Non-aqueous electrolyte cell, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Non-aqueous electrolyte cell will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2468121