With　the　capacity　of　energy　conversion　from　heat　to　electricity　directly,　thermoelectric　materials　have　been　considered　as　an　alternative　solution　to　global　energy　crisis.　In　this　work,　Cu　modified　Bi0.5Sb1.5Te3　(BST)　composites　are　prepared　by　a　facile　electroless　plating　Cu　method,　spark　plasma　sintering,　and　annealing.　The　annealed　0.22wt.%Cu/BST　has　an　enhanced　peak　Figure　of　Merit　(zT)　of　similar　to　0.71　at　573　K　with　high　average　zT　of　0.65　in　the　wide　temperature　range　between　300　and　573　K.　Due　to　the　significant　increase　of　electrical　conductivity　and　low　lattice　thermal　conductivity,　the　annealed　0.22wt.%Cu/BST　shifts　peak　zT　to　high　temperature,　and　shows　492%　enhancement　than　that　of　pristine　BST　with　zT　of　0.12　at　573　K.　Through　detailed　structural　characterization　of　the　annealed　0.22wt.%Cu/BST,　we　found　that　Cu　can　dope　into　BST　matrix　and　further　form　Cu2Te　nanoprecipitates,　dislocations,　and　massive　grain　boundaries,　leading　to　a　low　lattice　thermal　conductivity　of　0.30　Wm(-1)　K-1　in　the　annealed　0.22wt.%Cu/BST.　Such　enhanced　peak　zT　in　high-temperature　and　high　average　zT　in　the　wide　temperature　range　shows　that　the　electroless　plating　Cu　method　and　annealing　can　improve　the　thermoelectric　performance　of　commercial　BST　and　expand　the　applicability　of　Bi2Te3　thermoelectric　materials　in　the　power　generations.