Suchergebnisse

We report the exfoliation of layered Na2Ti3O7, a promising anode material for Na-ion batteries, and restacking using HNO3and NaOH to form H-[Ti3O7] and Na(x)-[Ti3O7] compositions, respectively. The materials were characterized by a range of techniques (SEM, TEM, solid-state NMR, XRD, PDF). Although the formation of aggregated nanoparticles is favored under acidic restacking conditions, the use of basic conditions can lead to control over the adherence between the exfoliated layers. Pair distribution function (PDF) analysis confirms that the local TiO6connectivity of the pristine material is maintained. The lowest sodium-containing phase Na(1)-[Ti3O7], which is the stable product upon Na+leaching after consecutive washing steps, displays the best performance among the compositions studied, affording a stable reversible capacity of about 200 mAh·g-1for 20 cycles at a C/20 rate. Washing removes the excess of "free/reactive" Na+, which otherwise forms inactive Na2CO3in the insufficiently washed compositions. ; M.A.T, A.J.P, J.M.S, and R.N.K. acknowledge funding from the United States Department of Energy (DOE, funder reference: 7057154). P.K.A. acknowledges a Junior Research Fellowship from Gonville and Caius College and an Oppenheimer Fellowship from the University of Cambridge. European Union's Horizon 2020 research and innovation programme under grant agreement No. 696656–GrapheneCore1 (G.K.)