Oppvarming av litium- og litiumionceller

Abstract

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.