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Li-rich layered oxides (LLOs) as cathode materials are expected to be applied to advanced lithium-ion batteries (LIBs) with great potential. However, the electrochemical instability and large voltage decay seriously restrict their development. In this work, a novel LLO cathode material (SN-LLO) with Sn and Na co-doping is fabricated through a co-precipitation process with subsequent calcination, which exhibits enhanced electrochemical stability and suppressed voltage decay. Structural characterizations indicate that with the regulation of Na doping, the impurity Li2SnO3 is inhibited and layered SN-LLO solid solution with the √3x√3-R30° arrangement of Sn in layers and stacking faults along c axis is obtained. DFT calculations demonstrate that the enhanced electrochemical stability results from the increase in the energy barrier of Mn migration in the slabs due to the steric effect of Sn. This study provides a rational design idea to improve the electrochemical stability of advanced Li-rich layered oxides. [ABSTRACT FROM AUTHOR]