Polyhierarchically structured TiP2O7/C microparticles with enhanced electrochemical performance for lithium-ion batteries

Abstract

Polyanionic compounds with a three-dimensional (3D) framework structure have attracted much interest in the role of electrode materials for organic and/or aqueous lithium-ion batteries due to their relatively high lithium-ion mobility, competitive energy density, good thermal/electrochemical stability, and low cost. In this paper, polyhierarchically structured TiP₂O₇/C microparticles constructed by carbon-coated nanoflakes encasing crystalline nanoparticles have been prepared by directly annealing flower-like titanium hydrogen phosphate hydrate (Ti(HPO₄)₂·xH₂O, THPH) microparticles, which are produced with tetrabutyl titanate and phytic acid in an ethanol-thermal medium. A reasonable formation mechanism of the flower-like THPH microparticles is proposed on the basis of time-dependent experimental results and theoretical calculations. The carbon layer plays a crucial role in the formation of TiP₂O₇/C polyhierarchical architecture. When cycled at 1 C for 100 cycles, 2 C for 200 cycles, and 5 C for 400 cycles, the TiP₂O₇/C microparticles exhibit exceptional reversible specific capacities of 128, 123, and 90 mA h g⁻¹ with capacity retention of 95.1%, 93.2%, and 94.4%, respectively. The high performance is attributed to interfacial Li storage and fast Li-ion diffusion due to the polyhierarchical architecture with carbon nano-coating and 3D open pores.