TiP₂O₇-Covered Carbon Nanosheets as Anode Materials for Lithium-Ion Batteries with a High Rate and Improved Coulombic Efficiency

Abstract

The typical polyanionic-based material of TiP 2 O 7 can alleviate the volume change caused by repeated insertion/ extraction of lithium ions. However, the strong P−O covalent bond leads to sluggish electron transfer kinetics, limiting its rate capability. Here, TiP 2 O 7 -covered reduced graphene oxide (TiP 2 O 7 /rGO) is synthesized by facile ball milling and subsequent annealing. The close contact of TiP 2 O 7 with rGO accelerates the transfer of electrons and lithium ions, contributing to the reduced interfacial charge transfer impedance and superhigh pseudocapacitance. Therefore, the TiP 2 O 7 /rGO composite shows excellent rate capability, with capacities of 525.7, 465.3, 427.0, 391.9, 352.8, 286.8, and 172.5 mAh g −1 at current densities of 0.1, 0.2, 0.5, 1, 2, 5, and 10 A g −1 . The wrapping of rGO nanosheets helps to reduce the irreversible insertion of lithium ions and form a stable solid electrolyte interphase film, which gives the TiP 2 O 7 /rGO composite a superior initial coulombic efficiency of 61.89% and outstanding cyclic stability with a reversible capacity of 381.2 mAh g −1 after 1000 cycles at 1 A g −1 . The results suggest an effective strategy for advanced TiP 2 O 7 -based anodes for lithium-ion batteries.