Lithium-ion batteries Runaway risk of forming toxic compounds

Lithium-ion batteries are stabilized by an ultrathin protective film that is 10-50 nanometres thick and coats both electrodes. Here we artifically simulate the 'thermal-runaway' conditions that would arise should this coating be destroyed, which could happen in a battery large enough to overheat beyond 80 °C. We find that under these conditions the reaction of the battery electrolyte with the material of the unprotected positive electrode results in the formation of toxic fluoro-organic compounds. Although not a concern for the small units used in today's portable devices, this unexpected chemical hazard should be taken into account as larger and larger lithium-ion batteries are developed, for example for incorporation into electric-powered vehicles.