Current　studies　of　cathodes　for　potassium　batteries　(PBs)　mainly　focus　on　the　intercalation-type　materials.　The　conversion-type　materials　that　possess　much　higher　theoretical　capacities　are　rarely　discussed　in　previous　literatures.　In　this　work,　carbon　fluoride　(CFx)　is　reported　as　a　high　capacity　conversion-type　cathode　for　PBs　for　the　first　time.　The　material　delivers　a　remarkable　discharge　capacity　of　>250　mAh　g−1　with　mid-voltage　of　2.6　V　at　20　mA　g−1.　Moreover,　a　highly　reversible　capacity　of　around　95　mAh　g−1　is　achieved　at　125　mA　g−1　and　maintained　for　900　cycles,　demonstrating　its　excellent　cycling　stability.　The　mechanism　of　this　highly　reversible　conversion　reaction　is　further　investigated　by　nuclear　magnetic　resonance　spectra,　X-ray　diffraction,　and　transmission　electron　microscopy　studies.　According　to　the　analyses,　the　C-F　bond　in　the　cycled　material　is　different　from　that　in　the　pristine　state,　which　presents　relatively　higher　reversibility.　This　finding　offers　important　insights　for　further　improving　the　performance　of　the　CFx.　This　work　not　only　demonstrates　the　CFx　as　a　high　performance　cathode　for　PBs,　but　also　paves　a　new　avenue　of　exploring　conversion-type　cathodes　for　high　energy　density　PBs.　©　2020　Science　Press