N-doped foam flame retardant polystyrene derived porous carbon as an efficient scaffold for lithium-selenium battery with long-term cycling performance

•Hierachically porous carbon has been fabricated by foamed polymer.•After selenization, Se was implanted into the hierachically porous carbon.•The as-prepared composite exhibited excellent rate capability and cycle stability.•The capacity was up to 917.8 mAh g−1 at 1 A g−1 after 600 cycles.