Carbon nanofoam paper enables high-rate and high-capacity Na-ion storage

Carbon nanofoams (CNF) fabricated within carbon-fiber paper are investigated as negative electrodes for electrochemical Na-ion storage. In electrolyte-limited half-cell testing vs. sodium metal, these freestanding, ultraporous electrode architectures deliver specific capacity >200 mA h g(CNF)(-1) at a 1C rate and >150 mA h g(CNF)(-1) at 10C. The outstanding charge-storage capacity is a consequence of the high defect concentration inherent to the amorphous carbon nanofoam, which maximizes a capacitively controlled sodiation mechanism, while the through-connected pore structure of the CNF facilitates high-rate capability. We also compare the electrochemical performance of two pore-solid architectural variants of CNF paper electrodes.