Lithium-rich　layered　oxides　(LLOs)　are　prospective　cathode　materials　for　next-generation　lithium-ion　batteries　(LIBs),　but　severe　voltage　decay　and　energy　attenuation　with　cycling　still　hinder　their　practical　applications.　Herein,　a　series　of　full　concentration　gradient-tailored　agglomerated-sphere　LLOs　are　designed　with　linearly　decreasing　Mn　and　linearly　increasing　Ni　and　Co　from　the　particle　center　to　the　surface.　The　gradient-tailored　LLOs　exhibit　noticeably　reduced　voltage　decay,　enhanced　rate　performance,　improved　cycle　stability,　and　thermal　stability.　Without　any　material　modifications　or　electrolyte　optimizations,　the　gradient-tailored　LLO　with　medium-slope　shows　the　best　electrochemical　performance,　with　a　very　low　average　voltage　decay　of　0.8　mV　per　cycle　as　well　as　a　capacity　retention　of　88.4%　within　200　cycles　at　200　mA　g(-1).　These　excellent　findings　are　due　to　spinel　structure　suppression,　electrochemical　stress　optimization,　and　Jahn-Teller　effect　inhibition.　Further　investigation　shows　that　the　gradient-tailored　LLO　reduces　the　thermal　release　percentage　by　as　much　as　about　41%　when　the　battery　is　charged　to　4.4　V.　This　study　provides　an　effective　method　to　suppress　the　voltage　decay　of　LLOs　for　further　practical　utilization　in　LIBs　and　also　puts　forward　a　bulk-structure　design　strategy　to　prepare　better　electrode　materials　for　different　rechargeable　batteries.