Over-current protection device

An over-current protection device, comprising:

• a first metal layer;
• a second metal layer;
• and
• a heat-sensitive layer laminated between the first metal layer and the second metal layer, the heat-sensitive layer exhibiting a positive temperature coefficient (PTC) characteristic and comprising:
• a first polymer consisting of polyvinylidene difluoride (PVDF), wherein PVDF has a plurality of crystalline phases comprising α-PVDF, β-PVDF and γ-PVDF, wherein the total amount of α-PVDF, β-PVDF and γ-PVDF is calculated as 100%, and the amount of α-PVDF accounts for 48% to 55%;
• and
• a conductive filler comprising a metal-ceramic compound and dispersed in the first polymer, thereby forming an electrically conductive path in the heat-sensitive layer.