Catalytic　conversion　of　polysulfides　has　been　regarded　as　an　effective　strategy　to　suppress　the　shuttle　effect　in　lithium-sulfur　(Li-S)　batteries　by　accelerating　the　conversion　of　lithium　polysulfides　(LiPSs).　However,　the　rational　design　of　high-performance　sulfur　electrocatalysts　still　remains　a　big　challenge.　In　this　work,　we　develop　a　facile　approach　to　synthesize　a　grain-boundary-rich　cobalt　selenide　hollow　multi-shelled　structure　(denoted　as　GB-CoSe　HoMS)　to　serve　as　a　high-efficiency　electrocatalyst　for　Li-S　batteries.　Such　a　unique　structural　design　could　physically　inhibit　the　diffusion　of　polysulfide　intermediates　and　effectively　accommodate　the　large　volume　expansion.　Besides,　the　GB-CoSe　HoMS　possesses　strong　chemical　adsorption　towards　LiPSs　and　superior　catalytic　activity　to　accelerate　the　conversion　reaction　kinetics,　thereby　suppressing　the　shuttle　effect　of　LiPSs　and　enhancing　the　sulfur　utilization.　Owing　to　the　multifarious　advantages,　the　assembled　Li-S　batteries　with　GB-CoSe　HoMS　modified　polypropylene　separators　display　a　high　initial　discharge　capacity　of　1393.3　mA　h　g−1　at　0.1C,　superior　rate　performance　(660.9　mA　h　g−1　at　3C),　and　good　long-term　cycle　stability　with　a　low　capacity　decay　rate　of　0.046%　per　cycle　after　1000　cycles　at　1C.　More　significantly,　even　with　a　high　sulfur　loading　of　5.5　mg　cm−2　and　lean　electrolyte　(E/S　≈　8.0　μL　mg−1),　the　battery　still　harvests　a　high　discharge　capacity　of　977.8　mA　h　g−1　after　40　cycles　at　0.2C,　suggesting　its　great　potential　for　practical　applications.　The　present　work　demonstrates　the　importance　of　engineering　the　morphology　and　grain　boundary　in　developing　high-performance　electrocatalysts　for　Li-S　batteries.　©　2024　The　Royal　Society　of　Chemistry.