US Patent 8003241 Lithium battery with external positive thermal coefficient layer

A lithium-ion battery includes a first terminal in electrical communication with a first electrode of the battery, a second terminal in electrical communication with a second electrode of the battery, a cell casing that includes a lid electrically connected to the cell casing, and a positive thermal coefficient (PTC) layer in electrical communication with the first terminal and over the lid of the cell casing. A battery pack includes a plurality of such lithium-ion batteries as described above.