NOVELTY - The device (100) has conductive leads (31,32) attached to electrode layers (21, 22). Heat-sink layers (41, 42) of a heat dissipating and electrically insulative material are attached to and covering a corresponding a pair of one of the electrode layers and an end portion (311) of one of the conductive lead and a pair of another one of the electrode layers and an end portion (321) of another one of the conductive lead. The heat dissipating and electrically insulative material includes a thermal conductivity greater than 1.7 watts per meter kelvin.    USE - Over-current protection device i.e. PTC device such as resettable fuse, for use in a battery assembly (claimed).    ADVANTAGE - The heat sink-layers of the heat dissipating and electrically insulative material comprise a thermal conductivity greater than 1.7 watts per meter kelvin in the device, so that a hold current of the device is significantly increased without increasing a surface area of the device, thus protecting a battery assembly in an efficient manner.    DETAILED DESCRIPTION - The heat dissipating and electrically insulative material is selected from a group consisting of epoxy-based composite material, acrylic-based composite material and polyester-based composite material. The device includes a positive temperature coefficient (PTC) element (1) that is made from PTO composition that contains a particulate conductive filler (11) that is made from a material selected from the group consisting of titanium carbide, zirconium carbide, vanadium carbide, niobium carbide, tantalum carbide, chromium carbide, molybdenum carbide, tungsten carbide, titanium nitride, zirconium nitride, vanadium nitride, niobium nitride, tantalum nitride, chromium nitride, titanium disilicide, zirconium disilicide, niobiumdisilicide, tungsten disilicide, gold, silver, copper, aluminum, nickel, nickel-metallized glass beads, nickel-metallized graphite, titanium-tantalum solid solution, tungsten-titanium-tantalum-chromium solid solution, tungsten-tantalum solid solution, tungsten-titanium-tantalum-niobium solid solution, tungsten-titanium-tantalum solid solution, tungsten-titanium solid solution and tantalum-niobium solid solution.    DESCRIPTION OF DRAWING(S) - The drawing shows a partly sectional view of a battery assembly.    PTC element (1)    Particulate conductive filler (11)    Electrode layers (21, 22)    Conductive leads (31, 32)    Heat-sink layers (41, 42)    Over-current protection device (100)    End portions of conductive leads (311, 312, 321, 322)