Microspherical carbon particles were prepared from a mixture of resorcinol and formaldehyde. The resulting gel was annealed at 950°C under an Ar atmosphere. The carbon microparticles exhibit a highly disordered structure and low specific surface area. A maximum reversible capacity of has been achieved in sodium cells, which is mainly developed ( ) below 0.2 V. magic-angle spinning nuclear magnetic resonance results show the interaction between reversibly inserted sodium and carbon. Several electrolytes have been tested, and it has been concluded that tetrahydrofuran solvent improves the electrochemical performance of these carbon microspheres in sodium cells.