O3-layered　metal　oxides　are　promising　cathode　materials　for　high-energy　Na-ion　batteries　(SIBs);　however,　they　suffer　from　fast　capacity　fade.　Here,　we　develop　a　high-performance　O3-Na-Ni0.68Mn0.22Co0.10O2　cathode　for　SIBs　toward　practical　applications　by　suppressing　the　formation　of　a　rock　salt　layer　at　the　cathode　surface　with　an　advanced　electrolyte.　The　cathode　can　deliver　a　high　specific　capacity　of　similar　to　196　mAh　g(-1)　and　demonstrates　＞80%　capacity　retention　over　1000　cycles.　NaNi0.68Mn0.22Co0.10O2-hard　carbon　full-cells　with　practical　loading　(＞2.5　mAh　cm-2)　and　lean　electrolyte　(similar　to　40　mu　L)　demonstrate　similar　to　82%　capacity　retention　after　450　cycles.　A　60　mAh　single-layer　pouch　cell　has　also　been　fabricated　and　demonstrated　stable　performance.　This　work　represents　a　significant　leap　in　SIB　development　and　brings　new　insights　to　the　development　of　advanced　layered　metal　oxide　cathodes　for　alkaline-ion　batteries.