Oxygen vacancies enhance the electrochemical performance of carbon-coated TiP2O7-y anode in aqueous lithium ion batteries

In this paper, a titanium pyrophosphate (TiP2O7) anode with oxygen vacancies is prepared by a simple one-pot solid method, exhibiting great performance. Herein, we study on the physical and chemical changes of TiP2O7-y with oxygen defect, and compare it with pure TiP2O7 through scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and so on. It is found that the introduction of oxygen vacancies leads an improved electronic conductivity compared to the pure TiP2O7 sample. Intriguingly, the TiP2O7-y with oxygen defect displays an enhanced electrochemical performance in aqueous lithium ion batteries (ALIBs), with a larger capacity of TiP2O7-y (57 mAh g(-1)) as compared to pure TiP2O7 (17 mAh g(-1)) at 0.2 A g(-1). After carbon-coating treatment, the C-TiP2O7-y anode demonstrates outstanding capacity and cycling performance with a capacity retention of 89% after 500 cycles at 0.5 A g(-1). More importantly, the full ALIBs coupled with LiMn2O4 cathode maintains 85% capacity after 800 cycles at 0.1 A g(-1). This study underscores the potential importance of incorporating oxygen vacancies into metal oxides as an alternative to modify the electrode materials in energy storage field. (C) 2019 Elsevier Ltd. All rights reserved.