LiNi0.5Co0.2Mn0.3O2　powders　synthesised　via　a　citric　acid　assisted　sol-gel　method　were　subsequently　surface-modified　with　graphene　oxide　using　a　wet　chemical　method.　X-ray　diffraction　(XRD)　results　showed　that　the　graphene-oxide-coated　LiNi0.5Co0.2Mn0.3O2　powders　exhibited　only　minor　differences　in　their　phase-structural　composition　compared　to　the　original　LiNi0.5Co0.2Mn0.3O2　powders.　The　graphene-oxide-　coated　LiNi0.5Co0.2Mn0.3O2　sample　presented　a　core-shell　structure,　with　a　uniform　coating　layer　with　a　thickness　of　about　1　nm　discovered　on　the　surface,　as　confirmed　by　field　emission　scanning　electron　microscopy　(FE-SEM)　and　transmission　electron　microscopy　(TEM).　X-ray　photoelectron　spectroscopy　(XPS)　revealed　that　the　transition　metals　(M　=　Ni,　Co,　Mn)　maintained　a　high　oxidation　state　after　surface　modification　with　graphene　oxide.　The　cycle　performance　of　the　graphene-oxide-　coated　LiNi0.5Co0.2Mn0.3O2　was　significantly　enhanced　at　a　high　temperature　of　55　degrees　C,　leading　to　a　capacity　retention　of　72%　after　100　cycles　compared　with　only　64%　for　the　bare　LiNi0.5Co0.2Mn0.3O2.　The　graphene-oxide-　coated　LiNi0.5Co0.2Mn0.3O2　also　demonstrated　better　performance　at　different　rates　than　the　pristine　sample.　The　effect　of　the　graphene　oxide　coating　layer　was　further　investigated　via　electro-chemical　impedance　spectroscopy　(EIS),　which　indicated　that　this　layer　plays　an　important　role　in　stabilising　the　interface　between　electrolyte　and　cathode　during　cycling.　(C)　2017　Elsevier　B.V.　All　rights　reserved.