Barium　titanate　(BaTiO3)-based　lead-free　relaxor　ferroelectric　ceramic　Ba0.65Sr0.245Bi0.07TiO3　was　developed　via　a　traditional　electrocremic　processing　technique　to　obtain　Pb-free　dielectric　bulk　ceramics　with　enhanced　energy　storage　performance　that　can　be　potentially　used　in　pulsed　power　devices.　The　added　CuO　can　broaden　the　phase　transition　peak,　and　move　it　to　lower　temperature,　reinforcing　the　dielectric　relaxor　behavior.　The　microstructure　evolution　of　the　sample　was　investigated　via　Piezoforce　microscopy,　and　the　corresponding　mechanism　regarding　the　electric　breakdown　strength　was　studied.　The　solubility　of　solid　CuO　in　the　Ba0.65Sr0.245Bi0.07TiO3　is　approximately　0.02　mol.　The　ceramic　sample　with　0.005　mol　CuO　possesses　160　kV/cm　electrical　breakdown　strength　and　an　energy　storage　efficiency　higher　than　76%,　which　yields　1.28　J/cm3　energy　storage　density.　Moreover,　the　ceramic　specimen　with　0.005　CuO　exhibits　relatively　good　temperature　stability,　good　frequency　stability　from　1　Hz　to　200　Hz,　and　also　good　fatigue　resistance　up　to　105　cycles,　and　can　be　a　potential　candidate　for　future　energy　storage　applications.　©　2019　Elsevier　Ltd　and　Techna　Group　S.r.l.