IE47359B1

IE47359B1 - An electric cell with an aprotic solution whose cathode active material is a bivalent lead oxide derivative

Info

Publication number: IE47359B1
Application number: IE2042/78A
Authority: IE
Original assignee: Accumulateurs Fixes
Priority date: 1977-10-14
Filing date: 1978-10-13
Publication date: 1984-02-22
Also published as: CA1096442A; FR2406312A1; JPS5465334A; NZ188630A; IE782042L; AU4065678A; NO149299B; BR7806748A; JPS5935148B2; AU516528B2; DK458278A; ES474185A1; NO783463L; IT1108107B; IT7869294A0; DE2860549D1; US4158723A; EP0001598A1; NO149299C; JPS59201369A

Abstract

A high specific energy electric cell having a lithium negative active material, an electrolyte solution of which the solvent is an aprotic liquid, and the positive active material is a derivative of divalent lead oxide, PbO. The lead oxide derivation is a compound of said PbO and an oxide selected from the group comprising the oxides of bismuth, Bi2O3, antimony, Sb2O3, and tin, SnO2. (From US4158723 A) [FR2406312A1]

Description

The present invention relates to high specific energy batteries having lithium as the negative active material and including an electrolyte in which the solvent is an aprotic composition. The invention relates particularly to a positive active material for such batteries.

French Patent No. 76 10 552 (published under No. 2,308,209) describes lithium batteries of which the active material comprises, bismuth oxide Bi2C>3 Further, French Patent No. 74 34 867 (published under 10 No. 2,288,401) and its certificate of addition No. 75 20 497 (published under No. 2,316,756) describe lithium batteries whose positive material comprises, among others, the oxide of lead having the formula Pb-^O^, or minium.

The Applicant has discovered that certain compositions, 15 analogous to minium, which result from the combination of an oxide having the character of an acidic anhydride with the oxide of lead, PbO, which itself has a basic character, give results at least equal to those of minium vzhen they are used as positive - 2 47359 active materials in lithium batteries.

The present invention thus has for its object an electric cell of which the negative active material is lithium, the electrolyte is a solution in which the solvent is an aprotic liquid, and the positive active material is a derivative of the divalent oxide of lead, PbO, wherein said derivative is a combination of said divalent lead oxide with an oxide of bismuth, BijOj.

The bismuthate of lead having a formula Pb^i^O^, among others, has given excellent results. This positive active material also has the following physical advantages: Its powder molds perfectly to form agglomerated electrodes, making it unnecessary to add a cinder, as is required in the case of minium; - It is much less soluble in propylene carbonate, among other solvents, and this permits the use of this electrolyte solvent for batteries which must be stored for a long time.

Electrolytes which can be used in batteries aceord20 ing to the invention are those solutions in which the solvent can be an ether or an ester or mixtures of ethers and esters. Among suitable ethers are dioxolane, tetrahydrofuran, dimethoxyethane, or their mixtures. Among suitable esters are dimethylsulf .ite, propylene carbonate, ethylene carbonate, etc.

The solute in sueh a battery is preferably a lithium salt, such as lithium perchlorate, lithium tetrafluoborate, -347359 lithium fluoromethylsulfonate, or lithium hexafluoroarsenate.

The invention can be better understood with the aid of the following examples, illustrated by the attached drawing in which Figure 1 is a cross-section of a battery structure useful for the practice of the invention and Figure 2 is a graph showing the discharge curves of two batteries, one battery according to the prior art and the other battery according to the invention.

Referring to Figure 1, conventional button-type batteries are constructed having an exterior diameter of 11.6 mm. and an overall height of 11.4 mm.

Tne battery casing is assembled from two cups, 1 and 7, of nickel steel or stainless steel, separated by a seal 8 of plastic or elastomeric material which serves both to seal and to insulate the cups electrically from each other. Negative cup 7 contains lithium in the form of a layer 5 deposited on a collector grill or screen 6 of nickel steel or stainless steel that is soldered or otherwise electrically bonded to the cup. The positive cup 1 contains powdered active material 2 which is augmented by an electronic conductor and, possibly, by a binder. This active mass is compressed into the cup 1 which may be equipped, as shown, with an annular metal ring 9 (made of nickel steel or stainless steel) which serves to contain the active material and also to reinforcingly support the seal 8, over which is crimped -447358 the lip of cup 1.

The positive and negative active materials are separated by a paper-barrier 3 and by layers of cellulose felt 4 saturated with an electrolyte. 1st embodiment according to the prior art: A first series of batteries was assembled on the model described above. The positive active mass was composed of powdered minium , to which was added powdered lead and polytetrafluoroethylene, in the respective weight 10 proportions of 73%, 23% and 4%. The mixed ingredients of this mass were then compressed into the positive cup under a 2 pressure of 1.5 tons/cm , the amount used providing a thickness of 1.35 mm for the cathode mass. The theoretical capacity of this mass was 148 mAh.

The electrolyte was composed of a 2 molar solution of lithium perchlorate in dioxolane. These batteries represented the technique of the prior art.

Each battery was discharged through a resistance of 5,000 ohms. Kith reference to Figure 2, curve A shows the discharge curve of these batteries, with the ordinate being calibrated in volts V and the abscissa being calibrated in hours of discharge time T.

Taking 1.2 volts as the final discharge voltage, the discharge time is about 550 hours, which corresponds to an effective capacity of 145 mAh. Xt should however be noted that, at discharge, for voltages from 1.3 to 1.2, it is quite probable that the polytetrafluoroethylene participates in the discharge and, as a consequence, the output is attributable to the mixture of minium and polytetrafluoroethylene. 2nd embodiment according to the invention: A second series of batteries similar to the first series was assembled, but having a positive active material according to the present invention. That active material was composed of bismuthate of lead, Pb2Bi2O,-.

To this was added powdered lead, as an electronic conductor, but the addition of a binder was rendered unnecessary by the compressible quality of the bismuthate powder. As a result, this active mass is more conductive than the mixture of minium and polytetrafluoroethylene, and the quantity of powdered lead can be decreased by about 10%.

The mass was, therefore, about 90% lead bismuthate and about 10% metallic lead, by weight. The compression of the active mass was carried out at 1 ton per cm2, to obtain a height of 1.35 mm. The theoretical capacity of this mass was 198 mAh.

With reference to Figure 2, curve B shows the discharge of these batteries through a resistance of 5,000 ohms. As can be seen, although the exterior dimensions of these cells are equal to the dimensions of those of the first example, the cells of this series using a positive active material according to the invention, discharged at a higher voltage (1.45 volts average, as against 1.37 average volts for the first series). Their discharge lasted for 600 hours, which corresponds to a capacity of 175 mAh.

It will be appreciated that the invention is not limited to the embodiments described and shown, Vihich are given only by way of example. - 6 47359

Claims

1. An electric cell having lithium as a negative active material, an electrolyte solution of which the solvent is a aprotic liquid, and a positive 5 active material derived from divalent lead oxide, PbO, wherein said derivative is a compound of PbO and an oxide of bismuth, Bi 2 O 3 .

2. An electric cell according to claim 1 wherein the positive active material is lead 10 bismuthate, Pb„Bi„O c . 2 2 b

3. An electric cell according to claim 1 or 2 wherein the positive active material further comprises an electronic conductor.

4. An electric cell according to claim 3 15 wherein said electronic conductor is powdered lead. -747359

5. Δη electric cell according to any one of the preceding claims wherein the solvent of said electrolyte is selected from the group comprising dioxolane, tetrahydrofuran, dimethoxyethane, dimethyl sulfite, 5 propylene carbonate, ethylene carbonate, and their mixtures.

6. An electric cell according to any one of the preceding claims wherein the solute of said electrolyte solution is a lithium salt selected from the group comprising 10 lithium perchlorate, lithium tetrafluoborate, lithium fluoromethylsulfonate, and lithium hexafluoroarsenate.

7. An electric cell according to any one of the preceding claims wherein the electrolyte is a 2 molar solution of lithium perchlorate in one litre of dioxolane. Dated this the ljth day of October, 197

8. F. R. KELLY & CO.