Na-ion batteries (NIBs) are potential candidates for electrical energy storage systems owing to the naturally abundant sodium resources. In contrast to Li-ion batteries (LIBs), the anodes of NIBs suffer from the slow kinetics of sodiation because of larger ion radius, which deteriorates their performance. In this work, the cationic vacancies are introduced by a solvothermal method to produce cation-deficient Ti0.84□0.16O1.42F0.37(OH)0.21 with improved sodium storage performance, showing a charge capacity (215 mAh g-1, 0.1C) and remarkable long-term cyclic stability (the capacity retention rate is 94.6% under 1C over 700 cycles). The insertion of Na ion into the vacancies and lattice gap without dramatic structure change is verified by in situ synchrotron-based X-ray diffraction (XRD) and ex situ high-resolution transmission electron microscopy (HRTEM). The introduced cationic vacancies are beneficial to accelerate sodium storage kinetics and to improve electrochemical performance. Th
Abstract
In this study, N-doped reduced graphene oxide (rGO) wrapped carbon micro fibres (CFs) were synthesized by one-step high temperature pyrolysis method. Free-standing binder-free electrodes of N-doped rGO on CF were fabricated to apply in extended flexible fibrous supercapacitors and sodium-ion batteries (NIBs). The results showed that the attachment of N-doped graphene onto CF led to high electrochemical capacitance properties. The micro-fibre electrodes showed high performance supercapacitor behaviour of 18.7 F cm at a current density of 1 A cm as a flexible solid-state energy storage device. In parallel with the supercapacitance properties, the micro-fibre electrode shows impressive electrochemical performances when evaluated as anode for NIB, delivering a reversible capacity of 400 mAh/g with capacity retention approaching 100% after 100 cycles. The excellent performances are attributed to defects induced by N-doping along with large surface area of hierarchical porous a