Transition-metal sulfides are of significant interest as rechargeable battery anodes owing to their low cost, wide availability, eco-friendliness, and high theoretical capacities. However, extraordinary structural changes in these materials cause pulverization of the electrode, thereby limiting their practical electrochemical abilities. Herein, a simple one-pot polyol refluxing method is used for fabricating a manganese sulfide (MnS) electrode composited with nitrogen and sulfur co-doped carbon (MnS@NS-C) for high-power lithium-ion batteries. This electrode exhibits unique spherical particle morphology with optimized average particle size (300 <x< 500 nm) and porous features. Owing to its nanostructure, porous nature, and an electrically conducting carbon network co-doped with heteroatoms, the composite electrode overcomes the strong structural variations to afford high practical storage capacities, long-term cycle stability, and outstanding rate capability. The MnS@NS-C electrode demonstrated high reversible storage capacities of 999 mA h g−1at 0.1 A g−1, the highest reversible capacity of 761 mA h g−1at 2 A g−1for over 300 cycles, and average rate capacities of 453 mA h g−1at 10 A g−1.In situsynchrotron X-ray diffraction investigations indicated a uniquely combined intercalation-cum-conversion reaction mechanism leading to β-Li2(1−x)MnS, Li2S, and Mn discharge products. The results of this study can provide deep insights into understanding intriguing reactions and motivate further study of transition-metal sulfides for prospective high-energy battery applications.