# US 4,397,919 A · Explosion resistant battery cells > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,397,919 A - Document ID: US4397919A - Status: Granted - Kind: A - Application number: 06/265,342 - Filed: 1981-05-19 - Granted: 1983-08-09 - Earliest claimed: 1979-03-22 - Assignees: The Standard Oil Company - Inventors: Geoffrey E. H. Ballard - Web page: https://patentgrep.com/patent/US4397919A ## CPC - H01M 50/174: adapted for the shape of the cells - H01M 6/14: Cells with non-aqueous electrolyte - H01M 50/342: Non-re-sealable arrangements - H01M 50/375: Vent means sensitive to or responsive to temperature - H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY ## Abstract An explosion resistant battery cell incorporating safety features adapted to counter the effects of the build-up of high internal pressures. The external metallic casing for the cell has a non-cylindrical cross-section which may be square, rectangular or other geometric configuration other than cylindrical to allow bulging of the outer walls which may result from internal pressure build-up. A thermal venting mechanism is provided in the nature of a low melting point metal plug inserted in the end of an associated electrolyte fill tube, the metal plug providing a hermetic seal but having a melting point considerably below the temperature at which explosion of the battery cell might occur depending on the electrolyte being used. ## Claims ### Claim 1 In an explosion resistant sealed battery cell having an electrolyte and an anode-cathode structure, the improvement comprising: a casing formed in a non-cylindrical configuration to render it distortable in shape by internal pressure to increase its volume, said non-cylindrical casing being made of a flexible material and having such dimensions and configuration to enable such volume expanding distortion without the creation of any breaks in the casing which would vent the interior thereof to atmosphere; and thermally responsive means associated with said cell for hermetically sealing the cell before and during volume expansion, said thermally responsive means being operable to melt at some pre-determined temperature associated with an internal pressure in excess of that causing volume expansion, melting of said thermally responsive means venting the casing to release excessive pressure from within said casing after the pressure induced volume expansion has taken place. ### Claim 2 (depends on 1) The battery cell of claim 1 wherein said non-cylindrical casing is made of stainless steel and has a relatively thin wall construction. ### Claim 3 (depends on 2) The battery cell of claim 2 wherein said stainless steel has minimum thickness of 0.010 inches. ### Claim 4 (depends on 1) The battery cell of claim 1 wherein said sealing means includes a material having a melting point lower than a pre-determined explosive temperature for said cell. ### Claim 5 (depends on 4) The battery cell of claim 4 wherein said material is made of a solder material having a low melting point. ### Claim 6 (depends on 4) The battery cell of claim 4 wherein said material is made of a metallic eutectic material. ### Claim 7 (depends on 1) The battery cell of claim 1 wherein the anode-cathode structure includes a permanently mounted electrolyte fill tube for introducing an electrolyte into the cell, and said thermally responsive sealing means comprises a plug of low melting point metallic material disposed in said fill tube. ### Claim 8 (depends on 1) The battery cell of claim 1 wherein the anode-cathode structure includes a permanently mounted electrolyte fill tube for introducing an electrolyte into the cell, and a plug of thermoplastic material disposed within and sealingly engaging the inner surface of said fill tube to provide a temporary seal. ### Claim 9 (depends on 8) The battery cell of claim 8 wherein said thermally responsive sealing means comprises a plug of low melting point metallic material which also is disposed in said fill tube at the outer end thereof. ### Claim 10 (depends on 8) The battery cell of claim 8 wherein the electrolyte in the cell contains sulphur dioxide. ### Claim 11 (depends on 8) The battery cell of claim 8 where said thermoplastic material plug is polyethylene or polypropylene. ### Claim 12 (depends on 1) The battery cell of claim 1 wherein a major portion of the electrolyte in the cell comprises sulfur dioxide. ### Claim 13 (depends on 1) The battery cell of claim 1 wherein the cell contains lithium, the electrolyte in the cell contains sulphur dioxide and the thermally responsive sealing means is made of a low melting point metallic material having a melting point lower than the melting point of lithium. ### Claim 14 A battery cell, comprising: a non-cylindrical casing constructed in a configuration and of a flexible material to expand its volume by bulging out its sides in response to otherwise explosive internal pressure levels within the casing, said casing material being sufficiently flexible to achieve such expansion without breaking open or otherwise venting the interior of the cell; an anode-cathode structure, including a permanently mounted electrolyte fill tube and an electrolyte contained within said casing; and a low melting point metalic plug fused to the inside of said fill tube for hermetically sealing said casing up to temperatures of a predetermined maximum, said plug being adapted to melt at said maximum temperature to unplug the fill tube and vent the interior of said casing to its surroundings for averting explosion of the cell after said casing has expanded its volume.