Europaisches Patentamt 19 European Patent Office Office europeen des brevets (n) Publication number: 0 422 966 B1 12 EUROPEAN PATENT SPECIFICATION @ Date of publication of patent specification <&) Int. CI.6 : H01M2/12 10.05.95 Bulletin 95/19 @ Application number: 90311276.1 (22) Date of filing : 15.10.90 @) Electrochemical cell having a safety vent closure. (§) Priority : 13.10.89 US 421440 @ Proprietor : EVEREADY BATTERY COMPANY, INC. Checkerboard Square (43) Date of publication of application St. Louis Missouri 63164 (US) 17.04.91 Bulletin 91/16 (72) Inventor : Chaney, Earl Jacob, Jr. @ Publication of the grant of the patent : 7606, Hidden Acres 10.05.95 Bulletin 95/19 Medina, OH 44256 (US) Inventor : O'Hara, Thomas James 28334 Osborn Road @ Designated Contracting States : Bay Village, OH 44140 (US) DE GB Inventor : Malay, Manuel Rafols 627 Salem Lane Brunswick, OH 44212 (US) (56) References cited : Inventor : Ayers, Alan Douglas EP-A- 0 490 080 28499 Stonegate Circle DE-A- 2 042 417 Westlake, OH 44145 (US) DE-B- 1 029 935 FR-A- 2 601 819 US-A- 3 555 370 (74) Representative : Lord, Hilton David et al US-A- 4 075 398 MARKS & CLERK, US-A- 4 296 186 57-60 Lincoln's Inn Fields US-A- 4 592 970 London WC2A 3LS (GB) US-A- 4 855 195 PATENT ABSTRACTS OF JAPAN, vol. 7, no. 170 (E-189)[1315], 27th July 1983 CO CO CO o> CM CM Note : Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been UJ filed until the opposition fee has been paid (Art. 99(1) European patent convention). Jouve, 18, rue Saint-Denis, 75001 PARIS 1 EP 0 422 966 B1 2 Description It is known that certain materials are capable of acting both as an electrolyte carrier, i.e., as solvent for The present invention relates to a non-resealable the electrolyte salt, and also as the active cathode for safety vent closure for nonaqueous liquid oxyhalide a nonaqueous electrochemical cell. Thus, the cell galvanic cells. 5 comprises an anode, a cathode collector and a cath- Galvanic cells may generate large quantities of ode-electrolyte, the cathode-electrolyte comprising a gas under certain conditions, during use of storage, solution of an ionically conductive solute dissolved in and since many such cells are required to be tightly an active cathode depolariser. The active cathode de- sealed in order to prevent loss of electrolyte by leak- polariser typically comprises a liquid oxyhalide of an age, high internal gas pressures may develop. Such 10 element of Group V or Group VI of the Periodic Table. pressures can cause leakage, bulging or even rupture Suitable nonaqueous liquid cathode materials in- of the cell's container, especially under abusive con- clude sulphuryl chloride, thionyl chloride, phosphorus ditions such as charging and exposure to a high tem- oxychloride, thionyl bromide, chromyl chloride, vana- perature environment, if not properly vented. dyl tribromide and selenium oxychloride. Thus, several different types of resealable pres- 15 Another class of liquid cathode materials is the sure relief vent valves have been devised and em- halides of elements of Group IV to Group VI of the ployed for releasing high internal gas pressures from Periodic Table. Suitable nonaqueous cathode materi- a sealed galvanic cell. One type of valve that has als include sulphur monochloride, sulphur monobro- commonly been used consists basically of a valve mide, selenium tetraf luoride, selenium monobromide, member, such as a flat rubber gasket, which is biased 20 thiophosphoryl bromide, vanadium pentafluoride, into a sealing position over a vent orifice by means of lead tetrachloride, titanium tetrachloride, tin dibro- a resilient member, such as a helical spring. The mide dichloride and tin tribromide chloride. spring is designed to yield at a certain predetermined The "Periodic Table", as referred to herein, is the internal gas pressure, momentarily breaking the seal Periodic Table of Elements as set forth on the inside and allowing the gas to escape through the vent ori- 25 back cover of the Handbook of Chemistry and Phys- fice. ics, 63rd Edition, The CRC Press Inc., Boca Raton, US-A-3,664,878 discloses a resealable vent Florida, USA, 1982-1983. comprising a resilient deformable ball of elastomeric It has been found that when employing high en- material positioned to overlie a vent orifice in the ergy density liquid cathode materials in nonaqueous cell's container. A retainer means positioned over the 30 cell systems, the cells exhibit higher voltages than ball maintains the ball in place over the vent orifice cells employing conventional aqueous systems. and in contact with a valve seal provided around the Thus, fewer cell units are required to operate any par- peripheral edge portions of the vent orifice, and com- ticular battery-powered device. In addition, many of presses and deforms the resilient ball into a flattened the halide and oxyhalide nonaqueous cells display configuration, thus forming a normally fluid-tight seal 35 relatively flat discharge voltage-versus-time curves. between the flattened ball and the valve seal. The re- These cells, then, can be employed to produce bat- silient ball is capable of undergoing further temporary teries that will provide a working voltage closer to a deformation upon build-up of a predetermined high designated cut-off voltage than is practicable with internal gas pressure in the container so as to mo- some conventional aqueous systems generally not mentarily break the seal and allow gas to escape 40 exhibiting flat discharge voltage-versus-time curves. through the vent orifice. However, it would be extremely disadvantageous US-A-4,855,195 describes a cell employing a if, in the use of halide and oxyhalide liquid cathode current collector-safety switch member which also nonaqueous cells, any of the oxyhalide, halide ortheir employs a safety vent arrangement. The vent ar- reaction products escaped from the cell. Any escape rangement includes a bushing and a vent ball tightly 45 of liquids and/or gases could cause damage to the de- located in the bushing and thereby slightly deforming vice employing the cell or to the surface of a compart- the walls of the bushing. The bushing includes an up- ment or shelf where the cell was stored. On the other per flange and a distinct wall of substantially uniform hand, if the seal of the cell is effectively permanently thickness. secured, then it is possible that the build-up of internal However, with the continuing development of so pressure within the cell, under abuse conditions, portable electrically powered devices, such as tape would cause the cell's container to rupture, possibly recorders and playback machines, radio transmitters causing property and/or bodily damage. and receivers, and the like, new types of reliable, long To prevent rupture of the cell's container resulting service-life cells or batteries have been developed. from possible internal pressure build-up caused un- These provide a long service life by utilising highly re- 55 der abusive conditions, it is again necessary to vent active anode materials, such as lithium, sodium and the cell at some predetermined pressure. It has been the like, in conjunction with high energy density non- reported that some oxyhalide cells, such as those em- aqueous liquid cathode materials and a suitable salt. ploying thionyl chloride and/or sulphuryl chloride, 2 3 EP 0 422 966 B1 4 should be vented at pressures below about 500 psl an external circumference smaller than the internal (3,450 kPa) and preferably between about 150 and circumference of the opening defined in the upper 300 psi (1,030 and 2,070 kPa). portion of the bushing and larger than the internal cir- US-A-4,329,405 discloses a safety blow-out vent cumference of the opening defined in the lower por- closure for galvanic cells, such as nonaqueous oxy- 5 tion of the bushing; said seal member force-fitted halide cells which comprises the employment of a within the lower portion of the bushing to seal the cell; conductive tubular member secured to the cell's wherein at least one of said bushing and said seal housing and surrounding a vent orifice therein. A de- member is resiliently deformable such that said seal formable member is force-fitted in the vent orifice and member will be at least partially expelled from the adapted to be at least partially ejected from the vent 10 vent opening upon a predetermined internal gas pres- orifice upon the build-up of a predetermined internal sure buildup within the cell to provide a vent for the gas pressure within the cell. cell, and wherein said vent is non-resealable. In some applications of this vent, the wall defining It is an advantage of the present invention that it the vent orifice in the cover may be subjected to cor- provides a non-resealable safety vent closure for rosion at the deformable member/wall interface. This 15 electrochemical cells, and specifically oxyhalide could roughen the wall surface, thereby increasing cells, that vents at a predictable, safe pressure. the coefficient of friction between the deformable It is another advantage of the present invention member and the wall of the vent orifice. Venting of the that it provides a non-resealable safety vent closure cell is then likely to occur at unpredictable pressures, for cylindrical cells employing, for example, liquid oxy- and it is possible that venting may be altogether pre- 20 halides as the active cathode material and having re- vented.