Co3O4 carbon nanofiber mats as negative electrodes for sodium-ion batteries

• Co3O4-CNF mats were synthesized by electrospinning and carbonation.
• Co3O4-CNF mats direct used as negative electrodes for sodium-ion batteries.
• Co3O4-CNF mats delivered a capacity of ~400 mA h g−1 at 0.5 C after 700 cycles.

Co3O4 carbon nanofiber (CNF) mats were synthesized by sol-gel electrospinning and carbonization. The tiny Co3O4 nanocrystals (~6.27 nm) are homogeneously embedded in CNFs predominantly ~150 nm in diameter. When applied as negative electrode for sodium-ion batteries (SIBs), Co3O4-CNF mat delivered an excellent cycling stability with reversible specific capacity of 400 mA h g−1 at 0.5 C until 700 cycles. This impressed cycling performance is attributed to the nanoconfinement of the high capacity Co3O4 nanocrystals into one-dimensional CNF network. Such a conductive CNF mat could not only used as buffering matrix to effectively release the mechanical strain originated from the Na ion insertion/extraction, but also prevent the aggregation of Co3O4 nanocrystals.

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