MoSe 2 grown on N,P-co-doped carbon nanosheets is synthesized by a solvothermal reaction followed with a high-temperature calcination. This composite has an interlayer spacing of MoSe 2 expanded to facilitate sodiumion diffusion, MoSe 2 immobilized on carbon nanosheets to improve chargetransfer kinetics, and N and P incorporated into carbon to enhance its interaction with active species upon cycling. These features greatly improve the electrochemical performance of this composite, as compared to all the controls. It presents a specific capacity of 378 mAh g −1 after 1000 cycles at 0.5 A g −1 , corresponding to 87% of the capacity at the second cycle. Ex situ Raman spectra and high-resolution transmission electron microscopy images confirm that it is element Se, rather than MoSe 2 , formed after the charging process. The interaction of the active species with modified carbon is simulated using density functional theory to explain this excellent stability. The superior rate capability, where the capacity at 15 A g −1 equals ≈55% of that at 0.5 A g −1 , could be associated with the significant contribution of pseudocapacitance. By pairing with homemade Na 3 V 2 (PO 4 ) 3 /C, this composite also exhibits excellent performances in full cells.

Double-walled Sb@TiO2- x nanotubes take full advantage of the high capacity of Sb, the good stability of TiO2- x , and their unique interaction, realizing excellent electrochemical performance both in lithium-ion batteries and sodium-ion batteries.

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