Lithium-rich　layered　oxides　are　believed　to　be　the　most　competitive　cathode　materials　for　next-generation　lithium-ion　batteries　(LIBs)　due　to　their　high　specific　capacity,　but　the　poor　cycle　stability　and　voltage　attenuation　severely　limit　their　commercial　applications.　In　this　paper,　a　simple　method　combining　surface　treatment　via　pyrolysis　of　polyvinyl　alcohol　(PVA)　and　potassium　ions　(K+)　doping,　is　designed　to　improve　the　above　defects　of　the　cobalt-free　Lithium-rich　material　Li1.2Mn0.6Ni0.2O2　(LMR).　The　insoluble　surface　byproduct　Li2CO3　and　amorphous　carbon　nanolayer　derived　from　the　pyrolysis　process　of　PVA　alleviate　the　corrosion　of　acidic　species　with　a　favorable　conductivity,　while　a　large　radius　of　K+　can　enlarge　the　space　of　the　lithium　(Li)　layer　to　facilitate　the　diffusion　of　Li+,　suppress　voltage　polarization,　and　synchronously　restrain　the　transformation　from　a　layered　structure　to　a　spinel-like　structure.　After　modification,　the　LMR　material　exhibits　a　great　initial　discharge　capacity　of　266.0　mAh　g−1　at　0.1C,　a　remarkable　rate　capability　of　159.1　mAh　g−1　at　5C　and　an　extremely　high　capacity　retention　of　98.5%　over　200　cycles　at　0.5C　with　a　small　voltage　drop.　©　2021　Elsevier　Inc.