Single-crystal (SC) morphology of lithium-rich manganese-based layered oxides (LLOs) cathode materials, due to their stable structure and absence of excess grain boundaries, holds promise for addressing issues such as oxygen loss and poor cycle stability in traditional polycrystalline (PC) cathode materials. In this study, a low-cobalt SC LLOs cathode material with excellent electrochemical performances is successfully synthesized by the molten salt method and the appropriate calcination temperature. The SC LLOs cathode calcined at 900 °C exhibits superior physical properties. Its particle size of D50 is 332 nm, which results in an optimal average Li+ diffusion coefficient (DLi+) value of 10−10.29 cm2 s−1. At C/10 (1C = 250 mA g−1), it delivers the first discharge capacity of 242 mAh g−1 with an initial Coulombic efficiency (ICE) of 73.8 %. After 200 cycles at C/3, it maintains the capacity retention of 80.8 %. This work extensively elaborates on the influence of calcination temperature on the particle size, physical properties and electrochemical stability of low-cobalt SC LLOs cathode materials, which would provide effective guidance for the design of high-performance SC cathode materials.