Preparation of binder-free MoP/SnO2 carbon fiber composites with Cu-mediated surface modification for high-rate sodium ion storage

Abstract

Nanofiber webs stacking with circular cross-section generally suffer from insufficient inter-fiber connection and thus poor electrical contact. Beyond regular 1D nanofibers, electrospinning is able to fabricate nanobelt webs with reinforced electron transfer for energy storage and conversion. Previously, we prepared quasi-2D belt-like fiber through electrospinning of PMo12-PPy-SnCl2-PVP-based solution (phosphomolybdic acid /polypyrrole /SnCl2 /polyvinylpyrrolidone) with freestanding property. Here, to boost the electrochemical performance, we proposed Cu-mediated surface engineering for construction of accessible active sites with balanced material components of MoP/SnO2 and carbon. As a result, thinner and porous belt-like fibers were obtained with high specific surface area (above 100 m2 g−1). The interfacial charge transfer was improved by superficial phosphides, as binder-free electrode the Cu-mediated MoP/SnO2 carbon fiber composite can deliver capacity above 200 mAh g−1 at 0.2 A g−1 under low mass loading (1.5–2.5 mg cm−2) and sustain capacity above 1.0 mAh cm−2 with loading around 5 mg cm−2 at 2 mA cm−2. Combined with ex-situ characterization, the sodiation process was probed.