Ultrasonic　driven　wireless　charging　technology　has　recently　gained　increasing　attention.　High-performance　potassium　sodium　niobate　[(K,　Na)NbO3,　KNN]　based　ceramics　and　its　potential　application　on　energy　harvesting　device　are　presented　in　this　work.　A　series　of　lead-free　0.964(K0.48Na0.52)Nb0.96Sb0.04O3-0.032(Bi0.5Na0.5)ZrO3-xBiFe0.9Co0.1O3　[KNNS-BNZ-xBFC]　piezo-ceramics　are　first　designed　and　prepared　to　search　for　good　piezoelectric　properties,　high　Curie　temperature　and　good　thermal　stability.　Through　content　tailoring,　the　KNNS-BNZ-0.004BFC　ceramic　presents　enhanced　piezoelectric　properties　via　the　construction　of　rhombohedral-tetragonal　phase　boundary　near　room　temperature.　Based　on　the　synthesized　ceramics,　a　high-output　flexible　ultrasound-based　wireless　energy　harvesting　device　is　further　designed　and　manufactured　to　establish　a　connection　among　ceramics　and　practical　application　in　lead-free　KNN-based　ceramics.　The　average　ultrasound　receiving　sensitivity　of　the　fabricated　device　is　calculated　to　be　~　1.5　Vpp·MPa−1,　demonstrating　the　superior　performances.　An　instantaneous　power　density　of　52.07　mW/cm2　has　been　obtained　from　the　incident　ultrasound　pressure　of　1.90　MPa.　Capacitor　charging　applications　and　the　feasibility　study　of　ex　vivo　characterizations　under　porcine　tissue　also　demonstrate　the　good　application　prospect　of　the　harvester.　The　above　results　exhibit　great　potential　of　the　environmentally　friendly　KNN-based　materials　to　be　integrated　in　the　implantable　device　for　safe　biomedical　applications.　©　2021　Elsevier　Ltd