Lithium-rich and Ni-rich cathode materials have been considered as the attractive candidate for their high capacitive performance, but usually exhibit poor rate performance and limited cycle life. Herein, a facile gaseous sulfur treatment was developed to uniformly create oxygen vacancies and replace oxygen with sulfur atoms at the surface region of lithium-rich and Ni-rich cathode materials. Such a treatment, when applied to typical Li- or Ni- rich materials such as Li1.2Ni0.13Co0.13Mn0.54O2 (LNCMO), Li1.2Ni0.2Mn0.6O2 (LNMO) and LiNi0.8Co0.1Mn0.1O2 (NCM811), could enhance significantly all their cycle and rate performance. For example, LNCMO@S obtained from LNCMO, could exhibit a capacity retention of 81.10% after 600 cycles at 0.5 C (compared with 65.78% of LNCMO after 200 cycles), together with an excellent rate performance of 174.8 mA h g−1 at 10 C (compared with 133.3 mA h g−1 of LNCMO), which is among the best performance for all Li-rich cathode materials. The revealed mechanism, where the partial replacement of O by S at the lattice surface significantly reduces oxygen partial pressure and also enhances the Li ion conductivity, might shed light on the comprehensive design and control of oxygen activity in transition-metal-oxide systems for Li-ion batteries with high energy and power density.