A flexible Mn0.5Ti2(PO4)3/C nanofiber film with superior cycling stability for potassium-ion batteries.

First-principles calculations indicate that Mn0.5Ti2(PO4)3 is more suited to potassium-ion storage because of its lower energy gap than that of KTi2(PO4)3. A flexible Mn0.5Ti2(PO4)3/C nanofiber film (F-MTP/C NFF) has been first synthesized via electrospinning and applied to potassium-ion batteries as a self-standing anode. An integral carbon conductive network, unique one-dimensional nanostructure, and exceptional mechanical flexibility give F-MTP/C NFF outstanding potassium-ion storage performance. Impressively, the self-standing F-MTP/C NFF electrode delivers a high specific capacity of 218 mA h g-1 at 0.02 A g-1 and shows ultra-long cycling stability of 2000 cycles at 1 A g-1. This work may give a new insight into developing NASICON-type Ti-based materials as flexible electrodes for potassium-ion batteries.