Designing　separators　with　excellent　electrolyte　wettability　is　of　great　significance　to　improve　the　electrochemical　behavior　of　lithium-ion　batteries　(LIBs).　Herein,　we　develop　a　sandwich-structured　separator　by　facile　in　situ　polymerization　of　polyaniline　(PANI)　on　the　both　sides　of　polypropylene　(PP)　separator.　The　introduction　of　PANI　coating　improves　the　electrolyte　wettability　of　the　PP　separators.　Consequently,　the　cells　equipped　with　this　sandwich-structured　separator　demonstrate　superior　electrochemical　performance　including　initial　capacity,　rate　performance,　and　cyclic　stability　compared　with　the　PP　separator.　This　work　may　provide　a　facile　approach　for　separator　modification　to　improve　the　performance　of　LIBs.