Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Include electrolyte chemically specified and method
Reexamination Certificate
1999-10-08
2003-05-20
Ryan, Patrick (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Include electrolyte chemically specified and method
C429S199000, C429S324000, C429S330000, C429S332000, C429S333000, C429S338000
Reexamination Certificate
active
06566015
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a battery electrolyte that can be used for the electrolyte of a battery, and a non-aqueous electrolytic secondary battery that can be used as a battery for electric cars and portable electronic devices.
2. Description of the Related Art
There is a need for technology that uses electrical power more effectively in consideration of energy conservation and environmental issues. In order to respond to this need, a means of storing electricity is required that is able to store large amounts of electricity and provide that stored electricity efficiently. Secondary batteries having a large discharge capacity and high discharge voltage while also being able to be repeatedly charged and discharged are optimum for use as such a means of storing electricity.
Lithium secondary batteries are one example of this type of secondary battery. In a lithium secondary battery, a charging reaction occurs during charging in which lithium ions are released from the positive electrode and occluded at the negative electrode during charging, while during discharging, a discharging reaction occurs in which lithium ions are released from the negative electrode and occluded at the positive electrode. In lithium secondary batteries, since both energy density and output density are high, a large discharge capacity and discharge voltage are obtained. In addition, lithium ion secondary batteries, in which a negative electrode active material composed of a carbon material is used for the negative electrode, are expected to be used for portable electronic devices, electric cars and other applications due to their long service life and excellent practicality.
In lithium secondary batteries, an electrolyte made by dissolving a supporting electrolytic (electrolytes salts) salt in an organic solvent is used as the electrolyte. The electrolyte of this type of non-aqueous electrolytic secondary battery may be made by dissolving a supporting electrolyte such as lithium hexafluorophosphate (LiPF
6
) in an organic solvent of a cyclic carbonate compound such as ethylene carbonate or propylene carbonate. Since cyclic carbonate compounds have a high dielectric constant, the energy density and output density of the battery can be made to be extremely high.
However, due to the high viscosity of cyclic carbonate compounds, the mobility of the lithium ions is low. Consequently, organic solvent in which low-viscosity linear-carbonate compounds such as dimethylcarbonate and diethylcarbonate are mixed into these cyclic carbonate compounds are widely used. However, these linear-carbonate compounds have the shortcomings of being low molecular weight compounds which makes them susceptible to volatilization.
In addition, although attempts have been made to add low molecular weight ether compounds to electrolyte for the purpose of lowering the viscosity of the electrolyte, not only do they have the disadvantage of lowering cycle characteristics, but also end up lowering incombustibility, thereby causing problems in terms of safety.
Therefore, Japanese Unexamined Patent Publication (Kokai) No. 7-282849 discloses the improvement of shelf life and cycle characteristics while also reducing volatility by containing an alkylene bis-carbonate compound in an electrolyte. However, simply containing an alkylene bis-carbonate compound alone makes it difficult to sufficiently increase the incombustibility of the electrolyte. Thus, although this electrolyte has the required safety, that safety is not adequate.
On the other hand, Japanese Unexamined Patent Publication (Kokai) No. 4-184870 and Japanese Unexamined Patent Publication (Kokai) No. 8-111238 disclose the improvement of safety by using an ester phosphate like a linear alkyl phosphate or cyclic phosphate, and an organic solvent such as a halogen compound.
However, when phosphate ester is used for the primary solvent, a side reaction occurs at the negative electrode interface during charging causing the occlusion of lithium ions to not proceed efficiently. As the result, the battery performance, such as the energy density and the charging and discharging efficiency often decrease significantly.
On the other hand, when ethylene carbonate is used for the primary solvent and a small amount of phosphate ester is added, although the battery performance is not affected and has the required safety, the battery has the problem that the safety decreases. Thus, it was very difficult to reconcile the performance and the safety of the lithium secondary battery.
In addition, there have been no secondary battery that include phosphate esters or halogen compounds and that exhibit an excellent battery performance at temperatures outside the room temperature.
The present invention has been attained in view of the above circumstances. An object of the present invention is to provide an electrolyte that can make the battery performance such as the energy density and output density excellent, can highly maintain the performance at temperatures outside room temperature, and is excellent in incombustibility.
Another object of the present invention is to provide a non-aqueous electrolyte, and a non-aqueous electrolytic secondary battery that has an excellent battery performance such as energy density and the charging and discharging efficiency, cycle characteristic, etc., can maintain the battery performance at temperatures outside room temperature, and also is excellent in safety.
Another object of the present is to provide a non-aqueous electrolyte, and a non-aqueous electrolytic secondary battery in which it is used, that satisfies both high battery performance and safety in good balance as a result of examining the composition, mixing ratio and so forth of a non-aqueous electrolyte solvent that retains the battery characteristics of secondary batteries and has a high level of safety.
SUMMARY OF THE INVENTION
A first aspect of the present invention is a battery electrolyte wherein a supporting electrolyte is dissolved in an organic solvent, characterized in that said organic solvent contains (a) a cyclic carbonate compound (b) at least one type of alkyl mono-carbonate compounds represented by chemical formula (1) and alkylene bis-carbonate compounds represented by chemical formula (2), and (c) a phosphorous-containing organic compound:
R
1
OC(═O)OR
2
(1)
wherein, substitution groups R
1
and R
2
represent identical or different alkyl groups, and at least one of these has at least three carbon atoms; and:
R
3
OC(═O)OR
4
OC(═)OR
5
wherein, substitution groups R
3
and R
5
represent identical or different alkyl groups and have 1 to 4 carbon atoms, and R
4
represents a straight chain or branched alkylene group having 1 to 3 carbon atoms.
Cyclic carbonate compounds are able to increase the dielectric constant and so forth of electrolytes. Consequently, they can be made to provide excellent battery characteristics such as being able to increase the energy density of the battery.
The alkyl mono-carbonate compound represented by chemical formula (1) is able to lower the viscosity of an electrolyte. Consequently, since this compound is able to increase the mobility of electrolyte ions and so forth, they can be made to provide excellent battery characteristics such as energy density and output density. In particular, this compound is able to enhance electrolyte performance at low temperatures since it is able to maintain the energy density of batteries at high levels even at low temperatures.
The alkylene bis-carbonate compound represented by chemical formula (2) is able to give the electrolyte excellent storage properties. This alkylene bis-carbonate compound is able to enhance electrolyte performance at high temperatures since it is able to give the electrolyte excellent storage properties at high temperatures, in particular.
The phosphorous-containing organic compound is able to increase the incombustibility of the electrolyte. Consequently, it is able to enhance the safety of the electrolytic salt.
Kubota Naohiro
Oikawa Tomoyuki
Takeuchi Yasunori
Yamada Manabu
Denso Corporation
Mercado Julian
Ryan Patrick
LandOfFree
Non-aqueous electrolytic salt and non-aqueous electrolytic... 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 electrolytic salt and non-aqueous electrolytic..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Non-aqueous electrolytic salt and non-aqueous electrolytic... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3030379