Oppvarming av litium- og litiumionceller

Lithium cells may for safety purposes be equipped with safety vents, shut down separators and various types of fuses. In this work lithium primary cells, lithium ion cells and a lithium ion polymer battery block have been heated to 250ºC at a rate of 4ºC/minute. Thus far above their recommended operating temperature. The results showed that fully charged cells with vent released their electrolyte (no flame observed) when heated above a certain temperature. Further heating, with two exceptions (Li/SO2 LO 26 SX and Li/SOCl2 LS 33600), resulted in a fire. A heating test was also performed on cells of 50% SOC. The cells type tested were: Li/SO2Cl2 (CSC93) as well as Li/SO2 (LO 26 SX )and Li/SOCl2 (LSH20). The 50% SOC CSC93 cell vented with flames where as the two other types behaved similar to fresh cells. A cell type (Li/SOCl2) with no vent was also heated. This cell type exploded violently at 227 o C (average of 4 experiments). A lithium ion cell of 0% SOC only vented when heated, where as fully charged cells will on further heating after venting, catch fire. A fully charged Li ion polymer battery consisting of parallel connected polymer cells moulded in a polyurethane block was also heated. At 300 OC a fissure in the mould occurred, allowing the electrolyte to evaporate. Self heating took place and at approximately 470 OC, flames were observed.