Non-aqueous electrolyte battery and charging method therefor

Details Non-aqueous electrolyte battery and charging method therefor Non-aqueous electrolyte battery and charging method therefor

1999-05-25

2001-11-13

Griffin, Steven P. (Department: 1754)

Chemistry: electrical current producing apparatus, product, and

Current producing cell, elements, subcombinations and...

Electrode

C429S218100, C429S224000, C429S231100, C429S231950, C429S303000, C429S306000

Reexamination Certificate

active

06316145

ABSTRACT:

TECHNICAL FIELD
The present invention relates generally to a non-aqueous electrolyte battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte. More particularly, the invention relates to a non-aqueous electrolyte battery and a charging method therefor characterized in that where titanium oxide or lithium titanate is used as a negative electrode material for negative electrode, a charge current is prevented from being partially consumed for the decomposition of the non-aqueous electrolyte thereby to ensure a high charge/discharge efficiency.
BACKGROUND ART
Recently, as one type of advanced batteries featuring high power and high energy density, non-aqueous electrolyte batteries of high electromotive force have been used. The non-aqueous electrolyte battery utilizes the non-aqueous electrolyte, such as a non-aqueous electrolyte solution, and a process of oxidation and reduction of lithium or the like.
Such a non-aqueous electrolyte battery has generally employed, as the negative electrode material for negative electrode, metallic lithium, lithium alloys such as a Li—Al alloy, a carbon material capable of intercalating/deintercalating lithium.
One problem encountered with the use of metallic lithium as the negative electrode material for negative electrode is that charging/discharging of the battery results in lithium dendrite growth on the negative electrode surface.
Where the lithium alloy such as Li—Al alloy is used as the negative electrode material for negative electrode, the dendrite growth does not occur. However, a low flexibility of the lithium alloy makes it difficult to fabricate a cylindrical battery wherein the negative electrode and the positive electrode, with a separator interposed therebetween, are wound into a roll.
Where the lithium alloy is used in a powdery form, a high reactivity of the lithium alloy results in a problem of difficult handling thereof. In addition, when a charge/discharge process is performed with such a lithium alloy used as the negative electrode, the charge/discharge process induces expansion/contraction of the lithium alloy, which produces a stress within the lithium alloy. This leads to another problem that the repeating of such charge/discharge processes causes destruction of the lithium alloy, resulting in capacity decline.
Where, on the other hand, the carbon material is used as the negative electrode material for negative electrode, the charge/discharge process causes less expansion/contraction of the carbon material than in the aforesaid case where the lithium alloy is used. However, some problems exist that the capacity of the carbon material is small than that of the lithium alloy and the initial charge/discharge efficiency is low.
Recently, there has been proposed, as in JP, 6-275263, A, the non-aqueous electrolyte battery which uses titanium oxide or lithium titanate as the negative electrode material for negative electrode together with a non-aqueous electrolyte solution, as the non-aqueous electrolyte, which solution is prepared by dissolving a lithium salt into a non-aqueous solvent.
Unfortunately, where titanium oxide or lithium titanate is used for the negative electrode in combination with the non-aqueous electrolyte solution prepared by dissolving the lithium salt into the non-aqueous solvent, a problem exists that the non-aqueous electrolyte solution is decomposed by a catalytic reduction induced by titanium oxide or lithium titanate contained in the negative electrode while the charge current is partially consumed for the decomposition of this non-aqueous electrolyte solution and hence, the charge/discharge efficiency is lowered.
In view of the foregoing, the invention is directed to solve the aforementioned problem encountered with the use of titanium oxide or lithium titanate as the negative electrode material for use in the negative electrode of the non-aqueous electrolyte battery including the positive electrode, the negative electrode and the non-aqueous electrolyte. An object of the invention is to provide a non-aqueous electrolyte battery which ensures a high charge/discharge efficiency by preventing the non-aqueous electrolyte from being decomposed by the catalytic reduction induced by titanium oxide or lithium titanate used for the negative electrode.
DISCLOSURE OF INVENTION
In accordance with the invention, a non-aqueous electrolyte battery using titanium oxide or lithium titanate as a negative electrode material for use in a negative electrode thereof is characterized in that a polymeric electrolyte is interposed between the negative electrode and a positive electrode.
If, as suggested by the invention, the polymeric electrolyte is interposed between the negative electrode and the positive electrode of the non-aqueous electrolyte battery using titanium oxide or lithium titanate as the negative electrode material for negative electrode, the polymeric electrolyte is less liable to be decomposed by the catalytic reduction induced by titanium oxide or lithium titanate in comparison with the conventional non-aqueous electrolyte solution. This avoids the problem suffered by the conventional non-aqueous electrolyte battery that the charge current is partially consumed for the decomposition of the non-aqueous electrolyte solution so as to lower the charge/discharge efficiency. Thus, the non-aqueous electrolyte battery featuring the high charge/discharge efficiency is provided.
It is to be noted here that the known titanium oxide and lithium titanate may be used as the negative electrode material for negative electrode. Examples of a usable negative electrode material include a rutile-type titanium oxide, an anatase-type titanium oxide, a spinel-type lithium titanate and the like. Above all, particularly preferred is the spinel-type lithium titanate featuring a layered structure, easy insertion/desertion of lithium ions and high charge/discharge efficiency.
In the non-aqueous electrolyte battery of the invention, the known positive electrode materials capable of intercalating/deintercalating lithium ions may be used as the positive electrode material for positive electrode. Examples of a usable positive electrode material include lithium-transition metal compound oxides containing at least one of manganese, cobalt, nickel, iron, vanadium and niobium. Above all, particularly preferred is manganese oxide containing lithium, which is less susceptible to ion deposition on titanium oxide or lithium titanate used for the negative electrode.
Where manganese oxide containing lithium is used as the positive electrode material, LiMnO
2
is preferably used for the purpose of easy fabrication of the battery whereas manganese dioxide containing Li
2
MnO
3
is preferably used for the purpose of increasing the battery capacity. The aforesaid manganese dioxide containing Li
2
MnO
3
may be obtained by heat-treating a mixture containing a lithium salt, such as lithium hydroxide, lithium nitrate, lithium phosphate, lithium carbonate, lithium acetate and the like, and manganese dioxide at temperatures in the range of between 300° C. and 430° C. The reason why the temperature for the heat treatment is limited within the range of between 300° C. and 430° C. is because Li
2
MnO
3
is not preferably generated at temperatures of less than 300° C. whereas the decomposition of manganese dioxide takes place at temperatures of more than 430° C.
In the non-aqueous electrolyte battery according to the invention, the known polymeric electrolyte generally used in the art may be interposed between the positive electrode and the negative electrode. Examples of a usable polymeric electrolyte include polyethylene oxide, polypropylene oxide, cross-linked polyethylene glycol diacrylate, cross-linked polypropylene glycol diacrylate, cross-linked polyethylene glycol methyl ether acrylate, cross-linked polypropylene glycol methyl ether acrylate and the like.
Exemplary solutes to be added to the polymeric electrolyte include the known solutes generally used in the art, such as lithium compounds like lithium trifluoromethane

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