A packaging for a flexible secondary battery that is wrapped around an outer surface of an electrode assembly of the flexible secondary battery, the packaging for a flexible secondary battery in a shape of a tube that is wrapped around the outer surface of the electrode assembly, the packaging for a flexible secondary battery comprising: a mechanical support layer ; a reduced graphene oxide (rGO) layer disposed on the mechanical support layer and including a plurality of reduced graphene oxide sheets; a heat shrink layer disposed on the reduced graphene oxide layer ; and a sealant layer disposed on the heat shrink layer , wherein reduced graphene oxide particles are stacked to form a reduced graphene oxide sheet; the plurality of reduced graphene oxide sheets in the reduced graphene oxide layer forms electrostatic interaction between adjacent reduced graphene oxide sheets, and forms the reduced graphene oxide layer; the reduced graphene oxide sheets form electrostatic interaction between the adjacent reduced graphene oxide sheets by medium of metal cation Li + , K + , Ag + , Mg 2+ , Ca 2+ , Cu 2+ , Pb 2+ , Co 2+ , Al 3+ , Cr 3+ , Fe 3+ , or two or more thereof, forming electrostatic interaction, including ionic bonding, with oxygen functional groups at the edge of the reduced graphene oxide particles. the packaging for a flexible secondary battery in a shape of a tube that is wrapped around the outer surface of the electrode assembly, the packaging for a flexible secondary battery comprising: a mechanical support layer ; a reduced graphene oxide (rGO) layer disposed on the mechanical support layer and including a plurality of reduced graphene oxide sheets; a heat shrink layer disposed on the reduced graphene oxide layer ; and a sealant layer disposed on the heat shrink layer , wherein reduced graphene oxide particles are stacked to form a reduced graphene oxide sheet; the plurality of reduced graphene oxide sheets in the reduced graphene oxide layer forms electrostatic interaction between adjacent reduced graphene oxide sheets, and forms the reduced graphene oxide layer; the reduced graphene oxide sheets form electrostatic interaction between the adjacent reduced graphene oxide sheets by medium of metal cation Li + , K + , Ag + , Mg 2+ , Ca 2+ , Cu 2+ , Pb 2+ , Co 2+ , Al 3+ , Cr 3+ , Fe 3+ , or two or more thereof, forming electrostatic interaction, including ionic bonding, with oxygen functional groups at the edge of the reduced graphene oxide particles. a mechanical support layer ; a reduced graphene oxide (rGO) layer disposed on the mechanical support layer and including a plurality of reduced graphene oxide sheets; a heat shrink layer disposed on the reduced graphene oxide layer ; and a sealant layer disposed on the heat shrink layer , wherein reduced graphene oxide particles are stacked to form a reduced graphene oxide sheet; the plurality of reduced graphene oxide sheets in the reduced graphene oxide layer forms electrostatic interaction between adjacent reduced graphene oxide sheets, and forms the reduced graphene oxide layer; the reduced graphene oxide sheets form electrostatic interaction between the adjacent reduced graphene oxide sheets by medium of metal cation Li + , K + , Ag + , Mg 2+ , Ca 2+ , Cu 2+ , Pb 2+ , Co 2+ , Al 3+ , Cr 3+ , Fe 3+ , or two or more thereof, forming electrostatic interaction, including ionic bonding, with oxygen functional groups at the edge of the reduced graphene oxide particles. <EOS>