Carbon microspheres obtained from resorcinol-formaldehyde as high-capacity electrodes for sodium-ion batteries

Microspherical carbon particles were prepared from a mixture of resorcinol and formaldehyde. The resulting gel was annealed at 950 degrees C under an Ar atmosphere. The carbon microparticles exhibit a highly disordered structure and low specific surface area. A maximum reversible capacity of 285 mAh g(-1) has been achieved in sodium cells, which is mainly developed (247 mAh g(-1)) below 0.2 V. Na-23 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. (C) 2005 The Electrochemical Society.