Flame-Retardant Composite Pad, Method for Manufacturing Same, and Secondary Battery Module and Secondary Battery Pack Comprising Such Composite Pad

There are provided a flame retardant element for suppressing flame propagation when a fire occurs during the use of a lithium secondary battery, thereby ensuring safety of the secondary battery while in use, a method for manufacturing the flame retardant element, and a secondary battery module and a secondary battery pack comprising the flame retardant element. The proposed flame retardant element is a composite pad having a stack of at least two polymer resin single layers including fire extinguishing materials having different fire extinguishing and flame retardant mechanisms, the composite pad includes a first polymer resin single layer and a second polymer resin single layer, and the first polymer resin single layer includes the fire extinguishing material which takes effect in a lower temperature range than the second polymer resin single layer.