GB2176927A - Electrical battery - Google Patents

Abstract

An electrical battery with a non-aqueous electrolyte comprising thionyl chloride or sulfuryl chloride and a metal salt dissolved therein and with an anode of a metal from group 1 or 2 in the Periodic Table or alloys of these, has reduced delayed action (D. A.) when the electrolyte contains SeO2 or TeO2 in concentrations up to saturation.

Description

SPECIFICATION Electrical battery The present invention concerns an electrical battery with a non-aqueous electrolyte/cathode comprising thionyl chloride or sulfuryl chloride and a metal salt dissolved therein and with an anode of a metal from group 1 or 2 in the Periodic Table or alloys of these.

A typical battery of this kind is the so-called lithium battery in which the electrolyte/cathode is thionyl chloride or sulfuryl chloride with lithium aluminum chloride (LiAlCI4) dissolved therein, and in which the anode is lithium.

Batteries of this kind have the drawback that during storage the anode metal builds up a passivating layer on the surface which causes so-called delayed action (DA), i.e. poor load carrying capacity of the battery at start.

Many attempts have been made to solve this problem but non has been able to eliminate delayed action without either increasing the self-discharge or the costs considerably. The attempts have concentrated on batteries in which the anode is lithium and will in the following be mentioned in connection with such battery, but in principle the problem is the same when the anode is one of the other metals from group 1 or 2 in the Periodic Table or alloys of these which are placed high in the electromotive series, seeing that delayed action is due to the formation of a layer of metal chloride on the surface of the anode which prevents the voltage producing reaction between the anode and the thionyl chloride or sulfuryl chloride from starting.This layer of metal chloride grows in the course of time, and if the battery has been stored for a very long time it may be so great that the battery is useless.

An attempt to solve the problem was to have the electrolyte contain sulfur dioxide (SO2) which has provided a good effect, both with electrolytes which are saturated and electrolytes which are unsaturated with lithium chloride (LiCI), but the effect maintains only at room temperature because the addition of SO, causes irreversible passivation if the battery is exposed to temperatures higher than about 40 C. Besides, the self discharge is considerably increased.

A second attempt was to replace the traditionally used salt LIAICI, with the salts Li2B10C110 and Li2B12C112.

Such change of the electrolyte gives rise to DA improvements but increases the costs of electrolyte considerably and results in a less stable and more poorly load carrying electrolyte.

A third attempt was to replace the salt LiAICI4 with the reaction product between NbCI5 and Li2S or Li2O. This too results in improvements of the DA properties of the battery, but so far it has only been ascertained in batteries which have been stored for a short period of time, seeing that the attempt is of a recent date.

Other additions to electrolytes which have turned out to result in DA improvement are addition of the salts SbCls and GaCI4. However, in themselves they do not give a satisfactory solution to the DA problem.

Finally, attempts have been made with coating of the lithium anode, but this method is troublesome and not very efficient.

Consequently, there is a need for an electrical battery of the type here in question which is free from delayed action problems and which does not have the drawbacks of poor load carrying capacity or self discharge either.

Such battery is provided by the present invention and it is characterised by the fact that the electrolyte contains SeO2 or TeO2 in concentration up to saturation.

By obtaining an effect by means of selenium dioxide or tellurium dioxide which is not accompanied by the above mentioned drawbacks of sulfur dioxide, selenium dioxide and tellurium dioxide have the advantage over sulfur dioxide that they are less aggressive to the glass sealing of the battery so that one avoids the leakage which may occur when a battery contains 802.

An especially advantageous effect is obtained when the electroylye/cathode also contains up to 0.9 M LiNbCl6 or LiTaCI6 seeing that these compounds reduce the self discharge of the cells without affecting the achieved DA improvements. A likely explanation of this may be that LiNbCl6 or LiTaCls form a stable lithium ion conducting passivation layer on lithium. When at the same time the growth of LiCI on this layer is prevented a dual effect is obtained where the cells have a very low self discharge at the same time as they are largely free from DA.

The invention is illustrated by the following examples in connection with the drawings.

Example 1 Some cells were prepared with lithium as the anode, thionyl chloride (SOCI2) as the electrolyte/cathode with 1.8 M LiAIC14 dissolved therein and carbon as the current collector.

The following amounts of 8002 were added to the thionyl chloride: Cell type 1: none (standard cell type) Cell type 2: 0.4% by weight of 5002 Cell type 3: 0.8% by weight of SeO2; moreover, a cell type 4 was prepared which contained in the electrolyte 1.20 M LiAlCI4; 0.60 M AlCi3; and SeO2 in an amount up to saturation.

Thereafter the cells were stored under the following conditions: Storage A: 2 weeks at 210C Storage B: 2 weeks at 700C Storage C: 5 weeks at 450C Storage D: 1 month at 700C and then their DA and capacity were measured.

Figures 1-4 of the drawing show the result of the DA measuring, the numbers of the graphs corresponding to the said cell types.

Figure 1 shows the results after storage for 2 weeks at 21 C.

Figure 2 shows the results after storage for 2 weeks at 70 C.

Figure 3 shows the results after storage for 5 weeks at 45 C.

Figure 4 shows the results after storage for 1 month at 700C.

After discharge the following capacites were found: Cell type Elh (V) Capacity (Ah) Storage 1 3.33 4.94 2 3.47 5.20 A 3 3.47 5.36 4 3.42 5.05 1 3.00 5.50 2 3.40 5.23 C 3 3.43 5.47 1 2.88 5.18 2 3.43 4.85 D 3 3.43 4.90 Example 2 6 cells were prepared with lithium as the anode, thionyl chloride as the electrolyte/cathode and carbon as the current collector, 2 of them with 1.8 M LIAICI, dissolved in the thionyl chloride, 2 with 1.8 M Li AICI4 and 0.8% by weight of SeO2 dissolved in the thionyl chloride, and 2 with 1.8 M UAICI, and 4% by weight of SO, dissolved in the thionyl chloride.

The cells were then stored for 2 months at 700 for checking leakage at the glass sealing.

The results were: Cell type Remarks 1.8 M LiAICI4 no leakage 1.8 M LIAICI, + 0.8 M % by weight SeO2 no leakage 1.8 M LIAICI, + strong leakage after 4% by weight SO, 3 weeks storage Example 3 Two cells were prepared with lithium as the anode, thionyl chloride as the electrolyte/cathode and carbon as the current collector, one of the celles with 1.8 M LIAICI, dissolved in the thionyl chloride, the other cell with 1.7 M LiAICI4; 0.1 M LiNbCI6; and 0.4% by weight of SeO2 dissolved in the thionyl chloride.

The cells were stored for 5 weeks at 450C whereafter they were discharged with the following result.

Cell type Elh (V) Capacity 1.8 M UAICI, 2.90 5.30 1.7 M UAICI, 0.1 M LiNbCI6 3.35 5.65 0.4% by weight SeO2 Example 4 Two cells were prepared with lithium as the anode, thionyl chloride as the active cathode, and carbon as current collector, one of the cells with 1.8 M LIAICI, dissolved in the thionyl chloride (standard cell), the other cells similarly with 1.8 M LIAICI, but also saturated with TeO2.

The cells were stored for 15 days at 700C whereafter DA was measured. The result of this measuring is shown in Figure 5 of the drawing, where the graph 1 is for the standard cell, and the graph 2 for the cell according to the invention.

Claims (6)

1. An electrical battery with a non-aqueous electrolyte/cathode comprising thionyl chloride or sulfuryl chloride and a metal salt dissolved therein and with an anode of a metal from group 1 or 2 of the Periodic Table or alloys of these, c h a r a c t e r i s e d in that that the electrolyte contains SeO2 or ToO2 in concentrations up to saturation.

2. An electrical battery as claimed in claim 1, c h a r a c t e r i s e d in that the electrolyte contains from 0.1 to 1.0% by weight of SeO2.

3. An electrical battery as claimed in claims 1 and 2, c h a r a c t e r i s e d in that the electrolyte in addition contains up 0.9 M LiNbC16 or LiTaCI6.

4. An electrical battery as claimed in claim 3, c h a r a c t e r i s e d in that the electrolyte contains from 0.02 to 0.30 M LiNbCI6 or LiTaCI6.

5. An electrical battery as claimed in claims 1-4, c h a r a c t e r i s e d in that the electrolyte is unsaturated with respect to LiCI.

6. An electrical battery substantially as described above and with reference to the accompanying drawing.