Development of sodium-ion batteries (SIBs) with greater energy density is of particular interest, but the anode choice is very limited, because of the failure of graphite in storing sodium. Although the alloying-type anodes demonstrate much higher capacity than the carbon anodes, the severe capacity fading hinders their applications. Herein, we present a novel alloying/conversion-based anode, where a conversion-type metal oxide (e.g., MnO) microdumbbell framework modified by a carbon layer was designed to stabilize the high-capacity alloying (e.g., Sn) nanoparticles. Combined with an electrolyte engineering approach, the as-designed Sn-MnO@C anode demonstrates a superior performance to store sodium, including a high capacity of 370 mAh g–1, extraordinary rate capacities over 10 A g–1, and a long lifespan of over 500 cycles. The high performance of the Sn-MnO@C anode in the SIB was further confirmed when the sodium vanadium phosphate-based cathode was paired. We demonstrate the importance of the synergistic effect of electrode structural design and electrolyte engineering (i.e., tuning Na+-solvent-anion complex) for attaining greater performance. This study opens a new avenue to preparing novel framework-supported functional materials and also offers a new opportunity to examine the electrolyte performance, facilitating the design of SIBs with greater power energy densities.