Na-Ion Storage Behaviors of Quadrangular Herringbone-Carbon Nanotubes in Ether- and Ester-Based Electrolyte Systems

Na-ion storage in graphitic carbons is a kinetically unfavorable process. It is envisioned that decreasing the size of graphitic layers can efficiently enhance Na-ion storage by shortening the diffusion pathway. However, because of the lack of model graphitic carbons, investigation on the effect of decreasing the graphitic layer size on Na-ion storage has not yet been carried out. In this work, quadrangular carbon nanotubes (q-CNTs) with herringbone-like graphitic walls are employed as model materials to exhibit the idea above. The q-CNTs show reduced dependence on the electrolytes. They deliver high capacity, excellent rate performance, and ultralong cyclic stability in both ether-based and ester-based electrolytes. Typically, the q-CNTs-600 exhibits high reversible capacities of 212 and 200 mA h g–1 at 0.1 A g–1 in ether-based and ester-based electrolytes, respectively. Even at 5 A g–1, the reversible capacity of 132 mA h g–1 can still be maintained in the ether-based electrolyte. The excellent Na-ion storage features of q-CNTs should be due to the herringbone-like graphitic walls and small graphitic layer size, which can weaken the control of electrolyte on the Na-ion diffusion kinetics by shortening the diffusion distance and providing more diffusion channels. Accordingly, these graphitic q-CNTs are expected to be promising anodes for sodium ion batteries